diff --git a/docu/README.md b/docu/README.md
new file mode 100644
index 0000000..f242092
--- /dev/null
+++ b/docu/README.md
@@ -0,0 +1,22 @@
+# Time Tracking and Management System Documentation
+
+# Time Tracking and Management System Documentation
+
+This document provides an overview of the Time Tracking and Management System. For detailed information, please refer to the following documents:
+
+- [General Overview](general_overview.md)
+- [Backend Architecture](backend_architecture.md)
+- [Frontend Architecture](frontend_architecture.md)
+- [Database Schema](database_schema.md)
+- [Deployment and DevOps](deployment_devops.md)
+- [Security and Privacy](security_privacy.md)
+- [Extensibility and Integrations](extensibility_integrations.md)
+- [LLM Guidance](llm_guidance.md)
+- [Roadmap](Roadmap.md)
+
+## Code Examples
+- [GORM Entities](code_examples/gorm_entities.go)
+- [FPGO Repository](code_examples/fpgo_repository.go)
+- [FPGO Service](code_examples/fpgo_service.go)
+- [API Handler](code_examples/api_handler.go)
+- [React Component](code_examples/react_component.tsx)
diff --git a/docu/Roadmap.md b/docu/Roadmap.md
new file mode 100644
index 0000000..b9a8289
--- /dev/null
+++ b/docu/Roadmap.md
@@ -0,0 +1,153 @@
+# Time Tracking System Roadmap
+
+This document outlines the roadmap for the development of the Time Tracking and Management System.
+
+## Project Phases
+
+### Phase 1: MVP (Minimum Viable Product)
+
+**Goal:** A functional system with core time tracking capabilities, user authentication, and basic project/activity management.
+
+**Sub-phases:**
+
+1.  **1.1 Core Backend Setup:**
+    -   Project initialization (Go, Next.js).
+    -   Database setup (PostgreSQL, GORM).
+    -   Basic API structure (Gin).
+    -   Authentication setup (JWT).
+
+2.  **1.2 User Management:**
+    -   User registration, login, and password management.
+    -   Implementation of basic user roles (User, Admin).
+
+3.  **1.3 Company Management:**
+    -   Company (tenant) creation and basic management (Admin only).
+
+4.  **1.4 Project and Activity Management:**
+    -   Project creation/editing/deletion (name, description, company association).
+    -   Activity creation/editing/deletion (name, billing rate, company association).
+
+5.  **1.5 Time Entry Core:**
+    -   Time entry creation (start/stop timer functionality).
+    -   Manual time entry input.
+
+6.  **1.6 Basic Frontend:**
+     - Basic UI for time entry.
+     - Basic UI for project/activity listing.
+
+7.  **1.7 Basic Listing and Filtering:**
+    -   Time entry listing.
+    -   Basic filtering (by user, project, date range).
+
+8.  **1.8 Simple Dashboard:**
+    -   Display of recent time entries.
+
+### Phase 2: Version 1
+
+**Goal:** Full implementation of the features described in the initial version of the specification.
+
+**Sub-phases:**
+
+1.  **2.1 Expanded Roles:**
+    -   Implement Manager, Auditor, and Company roles.
+
+2.  **2.2 Client and Employee Management:**
+    -   Client creation/editing/deletion.
+    -   Employee creation/editing/deletion (with hourly rates).
+
+3.  **2.3 Detailed Time Entry:**
+    -   Add fields for location, purpose, description, and billable percentage to time entries.
+
+4.  **2.4 Reporting Engine:**
+    -   Implement report generation (by project, employee, client, time period).
+    -   PDF export for reports.
+
+5.  **2.5 Dashboard Enhancements:**
+    -   Add graphical dashboards with summaries and visualizations.
+
+6.  **2.6 Tracker Improvement:**
+    -   Pre-populate tracker with data from the last booking.
+
+7.  **2.7 Multi-Tenancy Refinement:**
+    -   Ensure complete data isolation between tenants.
+
+8.  **2.8 RBAC Implementation:**
+    -   Implement fine-grained Role-Based Access Control.
+
+9.  **2.9 API Documentation:**
+    -   Create comprehensive API documentation using Swagger.
+
+10. **2.10 CI/CD Setup:**
+    -   Implement a basic CI/CD pipeline for automated testing and deployment.
+
+### Phase 3: Version 2
+
+**Goal:** Implement the "Future Enhancements" outlined in the specification.
+
+**Sub-phases:**
+
+1.  **3.1 Sprint and Task Management:**
+    -   Add sprint and task entities to the data model.
+    -   Implement sprint and task creation/editing/deletion.
+
+2.  **3.2 Kanban Boards:**
+    -   Develop Kanban board UI components.
+    -   Implement drag-and-drop functionality for task management.
+
+3.  **3.3 Task-Time Entry Linking:**
+    -   Allow users to select a specific task when creating a time entry.
+
+### Phase 4: Future Considerations
+
+**Goal:** Expand the system with additional features and integrations.
+
+**Sub-phases (Not exhaustive, can be further broken down):**
+
+1.  **4.1 Integrations:**
+    -   Billing systems integration.
+    -   Calendar integrations (Google Calendar, Outlook).
+    -   Project management tool integrations (Jira, Trello).
+    -   Webhook implementation.
+    -   SSO implementation.
+
+2.  **4.2 Extensibility:**
+    -   Develop a plugin system.
+    -   Implement custom fields.
+
+3.  **4.3 Mobile App:**
+    -   Develop responsive web design.
+    -   Explore native mobile app development.
+
+4.  **4.4 Internationalization:**
+    -   Implement multilingual support.
+    -   Add localized date/time formats.
+    -   Add currency conversion.
+
+5.  **4.5 Billing and Invoicing:**
+    -   Implement invoice generation.
+    -   Add billing data export functionality.
+    -   Implement reminders for unrecorded time.
+
+6.  **4.6 Notification System:**
+    -   Implement email and in-app notifications.
+    -   Add reminders and approval requests.
+
+7.  **4.7 Analytics:**
+    -   Implement advanced analytics and reporting.
+    -   Add trend analysis and forecasting.
+    -   Implement resource utilization tracking.
+    -   Add export options for BI tools.
+
+8. **4.8 Offline Functionality**
+    - Implement PWA features.
+    - Add local storage and synchronization.
+
+9. **4.9 Enhanced Security:**
+    - Implement more detailed audit trails.
+
+10. **4.10 Error Handling:**
+    - Implement a unified error handling and validation strategy.
+
+11. **4.11 Performance:**
+    - Implement Caching (Redis).
+    - Optimize database with indexing.
diff --git a/docu/backend_architecture.md b/docu/backend_architecture.md
new file mode 100644
index 0000000..0ebd94a
--- /dev/null
+++ b/docu/backend_architecture.md
@@ -0,0 +1,144 @@
+# Backend Architecture (Go)
+
+**Note:** This document describes a *conceptual* architecture and is not a final, binding requirement.
+
+The backend is written in Go and follows the principles of **Clean Architecture** and **Domain-Driven Design (DDD)**.
+
+## Project Structure
+```
+timetracker-backend/
+├── cmd/                               # Einstiegspunkte
+│   ├── api/
+│   │   └── main.go
+│   └── worker/
+│       └── main.go
+├── internal/                          # Interner Code
+│   ├── domain/                        # Domain Layer (DDD)
+│   │   ├── entities/                  # Domain Entitäten
+│   │   │   ├── user.go
+│   │   │   ├── company.go
+│   │   │   ├── project.go
+│   │   │   ├── timeentry.go
+│   │   │   ├── customer.go
+│   │   │   ├── activity.go
+│   │   │   ├── sprint.go
+│   │   │   ├── task.go
+│   │   │   └── kanban.go
+│   │   ├── repositories/              # Repository Interfaces
+│   │   │   ├── user_repository.go
+│   │   │   ├── company_repository.go
+│   │   │   ├── project_repository.go
+│   │   │   ├── timeentry_repository.go
+│   │   │   └── ...
+│   │   ├── services/                  # Service Interfaces und Implementierungen
+│   │   │   ├── auth_service.go
+│   │   │   ├── user_service.go
+│   │   │   ├── timetracking_service.go
+│   │   │   ├── reporting_service.go
+│   │   │   └── ...
+│   │   └── valueobjects/              # Value Objects
+│   │       ├── money.go
+│   │       ├── duration.go
+│   │       └── ...
+│   ├── application/                   # Anwendungsfälle
+│   │   ├── auth/                      # Authentication Use Cases
+│   │   │   ├── login.go
+│   │   │   ├── register.go
+│   │   │   └── ...
+│   │   ├── timetracking/              # Zeiterfassung Use Cases
+│   │   │   ├── create_time_entry.go
+│   │   │   ├── update_time_entry.go
+│   │   │   ├── list_time_entries.go
+│   │   │   └── ...
+│   │   ├── projects/                  # Projektverwaltung Use Cases
+│   │   │   └── ...
+│   │   ├── customers/                 # Kundenverwaltung Use Cases
+│   │   │   └── ...
+│   │   └── reporting/                 # Berichtswesen Use Cases
+│   │       └── ...
+│   ├── infrastructure/                # Infrastruktur
+│   │   ├── persistence/               # Datenbankzugriff
+│   │   │   ├── postgres/              # PostgreSQL Implementierung
+│   │   │   │   ├── connection.go
+│   │   │   │   ├── user_repository.go
+│   │   │   │   ├── company_repository.go
+│   │   │   │   └── ...
+│   │   │   └── migrations/
+│   │   ├── security/                  # Sicherheitsimplementierungen
+│   │   │   ├── jwt.go
+│   │   │   ├── password.go
+│   │   │   └── rbac.go
+│   │   ├── messaging/                 # Messaging-Implementierungen
+│   │   │   ├── email.go
+│   │   │   └── notification.go
+│   │   └── external/                  # Externe Dienste
+│   │       ├── calendar/
+│   │       ├── pdf/
+│   │       └── webhook/
+│   └── interfaces/                    # Interfaces
+│       ├── http/                      # HTTP-API
+│       │   ├── handlers/              # API Handler
+│       │   │   ├── auth_handler.go
+│       │   │   ├── user_handler.go
+│       │   │   ├── time_entry_handler.go
+│       │   │   └── ...
+│       │   ├── middleware/            # Middleware
+│       │   │   ├── auth_middleware.go
+│       │   │   ├── tenant_middleware.go
+│       │   │   ├── logging_middleware.go
+│       │   │   └── ...
+│       │   ├── dto/                   # Data Transfer Objects
+│       │   │   ├── auth_dto.go
+│       │   │   ├── user_dto.go
+│       │   │   ├── time_entry_dto.go
+│       │   │   └── ...
+│       │   └── routes/                # API Routes
+│       │       └── router.go
+│       └── grpc/                      # gRPC-API (Optional für Microservice-Kommunikation)
+├── pkg/                               # Öffentliche Pakete
+│   ├── functional/                    # FPGO Utilities
+│   │   ├── option.go
+│   │   ├── result.go
+│   │   └── ...
+│   ├── validator/                     # Validierung
+│   │   └── validator.go
+│   ├── logger/                        # Logging
+│   │   └── logger.go
+│   ├── errors/                        # Fehlerbehandlung
+│   │   └── errors.go
+│   └── utils/                         # Allgemeine Utilities
+│       ├── date.go
+│       ├── crypto.go
+│       └── ...
+├── api/                               # API Definitionen
+│   └── swagger/                       # Swagger Dokumentation
+│       └── swagger.yaml
+├── deployments/                       # Deployment-Konfigurationen
+│   ├── docker/
+│   │   ├── Dockerfile
+│   │   └── docker-compose.yml
+│   └── kubernetes/
+│       ├── api.yaml
+│       └── worker.yaml
+├── test/                              # Tests
+│   ├── unit/
+│   ├── integration/
+│   └── e2e/
+├── scripts/                           # Skripte
+│   ├── migration.sh
+│   ├── seed.sh
+│   └── ...
+├── docu/                              # Projektdokumentation
+│   ├── general_overview.md
+│   ├── backend_architecture.md
+│   ├── frontend_architecture.md
+│   ├── database_schema.md
+│   ├── security_privacy.md
+│   ├── extensibility_integrations.md
+│   ├── deployment_devops.md
+│   ├── llm_guidance.md
+│   └── README.md
+├── go.mod
+├── go.sum
+└── README.md
+```
diff --git a/docu/code_examples/api_handler.go b/docu/code_examples/api_handler.go
new file mode 100644
index 0000000..b83fac6
--- /dev/null
+++ b/docu/code_examples/api_handler.go
@@ -0,0 +1,101 @@
+// interfaces/http/handlers/time_entry_handler.go
+package main
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/username/timetracker/internal/application/timetracking"
+	"github.com/username/timetracker/internal/interfaces/http/dto"
+	"github.com/username/timetracker/internal/interfaces/http/middleware"
+)
+
+// TimeEntryHandler behandelt HTTP-Anfragen für Zeitbuchungen
+type TimeEntryHandler struct {
+	createTimeEntryUseCase *timetracking.CreateTimeEntryUseCase
+	updateTimeEntryUseCase *timetracking.UpdateTimeEntryUseCase
+	listTimeEntriesUseCase *timetracking.ListTimeEntriesUseCase
+	deleteTimeEntryUseCase *timetracking.DeleteTimeEntryUseCase
+}
+
+// NewTimeEntryHandler erstellt einen neuen TimeEntryHandler
+func NewTimeEntryHandler(
+	createTimeEntryUseCase *timetracking.CreateTimeEntryUseCase,
+	updateTimeEntryUseCase *timetracking.UpdateTimeEntryUseCase,
+	listTimeEntriesUseCase *timetracking.ListTimeEntriesUseCase,
+	deleteTimeEntryUseCase *timetracking.DeleteTimeEntryUseCase,
+) *TimeEntryHandler {
+	return &TimeEntryHandler{
+		createTimeEntryUseCase: createTimeEntryUseCase,
+		updateTimeEntryUseCase: updateTimeEntryUseCase,
+		listTimeEntriesUseCase: listTimeEntriesUseCase,
+		deleteTimeEntryUseCase: deleteTimeEntryUseCase,
+	}
+}
+
+// RegisterRoutes registriert die Routen am Router
+func (h *TimeEntryHandler) RegisterRoutes(router *gin.RouterGroup) {
+	timeEntries := router.Group("/time-entries")
+	{
+		timeEntries.GET("", h.ListTimeEntries)
+		timeEntries.POST("", h.CreateTimeEntry)
+		timeEntries.GET("/:id", h.GetTimeEntry)
+		timeEntries.PUT("/:id", h.UpdateTimeEntry)
+		timeEntries.DELETE("/:id", h.DeleteTimeEntry)
+	}
+}
+
+// CreateTimeEntry behandelt die Erstellung einer neuen Zeitbuchung
+func (h *TimeEntryHandler) CreateTimeEntry(c *gin.Context) {
+	var req dto.CreateTimeEntryRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Tenant-ID aus dem Kontext extrahieren
+	companyID, exists := middleware.GetCompanyID(c)
+	if !exists {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Company ID not found"})
+		return
+	}
+
+	// Benutzer-ID aus dem Kontext oder Request
+	var userID uuid.UUID
+	if req.UserID != nil {
+		userID = *req.UserID
+	} else {
+		currentUserID, exists := middleware.GetUserID(c)
+		if !exists {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "User ID not found"})
+			return
+		}
+		userID = currentUserID
+	}
+
+	// Command erstellen
+	cmd := timetracking.CreateTimeEntryCommand{
+		UserID:             userID,
+		ProjectID:          req.ProjectID,
+		ActivityID:         req.ActivityID,
+		TaskID:             req.TaskID,
+		StartTime:          req.StartTime,
+		EndTime:            req.EndTime,
+		Description:        req.Description,
+		BillablePercentage: req.BillablePercentage,
+	}
+
+	// UseCase ausführen
+	result := h.createTimeEntryUseCase.Execute(c.Request.Context(), companyID, cmd)
+	if result.IsFailure() {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": result.Error().Error()})
+		return
+	}
+
+	// TimeEntry in Response-DTO umwandeln
+	timeEntry := result.Value()
+	response := dto.MapTimeEntryToDTO(*timeEntry)
+
+	c.JSON(http.StatusCreated, response)
+}
diff --git a/docu/code_examples/fpgo_repository.go b/docu/code_examples/fpgo_repository.go
new file mode 100644
index 0000000..e8c693b
--- /dev/null
+++ b/docu/code_examples/fpgo_repository.go
@@ -0,0 +1,52 @@
+// domain/repositories/time_entry_repository.go
+package repositories
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/username/timetracker/internal/domain/entities"
+	"github.com/username/timetracker/pkg/functional"
+)
+
+// TimeEntryFilter enthält Filter für die Suche nach Zeitbuchungen
+type TimeEntryFilter struct {
+	UserID     *uuid.UUID
+	ProjectID  *uuid.UUID
+	CustomerID *uuid.UUID
+	StartDate  *time.Time
+	EndDate    *time.Time
+	ActivityID *uuid.UUID
+	TaskID     *uuid.UUID
+}
+
+// TimeEntryRepository Interface für den Zugriff auf Zeitbuchungen
+type TimeEntryRepository interface {
+	// FindByID sucht eine Zeitbuchung anhand ihrer ID
+	FindByID(ctx context.Context, companyID, id uuid.UUID) functional.Result[*entities.TimeEntry]
+
+	// FindAll sucht alle Zeitbuchungen mit optionalen Filtern
+	FindAll(ctx context.Context, companyID uuid.UUID, filter TimeEntryFilter) functional.Result[[]entities.TimeEntry]
+
+	// Create erstellt eine neue Zeitbuchung
+	Create(ctx context.Context, entry *entities.TimeEntry) functional.Result[*entities.TimeEntry]
+
+	// Update aktualisiert eine bestehende Zeitbuchung
+	Update(ctx context.Context, entry *entities.TimeEntry) functional.Result[*entities.TimeEntry]
+
+	// Delete löscht eine Zeitbuchung
+	Delete(ctx context.Context, companyID, id uuid.UUID) functional.Result[bool]
+
+	// GetSummary berechnet eine Zusammenfassung der Zeitbuchungen
+	GetSummary(ctx context.Context, companyID uuid.UUID, filter TimeEntryFilter) functional.Result[TimeEntrySummary]
+}
+
+// TimeEntrySummary enthält zusammengefasste Informationen über Zeitbuchungen
+type TimeEntrySummary struct {
+	TotalDuration         int
+	TotalBillableDuration int
+	TotalAmount           float64
+	TotalBillableAmount   float64
+	EntriesCount          int
+}
diff --git a/docu/code_examples/fpgo_service.go b/docu/code_examples/fpgo_service.go
new file mode 100644
index 0000000..f633bde
--- /dev/null
+++ b/docu/code_examples/fpgo_service.go
@@ -0,0 +1,99 @@
+// application/timetracking/create_time_entry.go
+package main
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/username/timetracker/internal/domain/entities"
+	"github.com/username/timetracker/internal/domain/repositories"
+	"github.com/username/timetracker/pkg/functional"
+	"github.com/username/timetracker/pkg/validator"
+)
+
+// CreateTimeEntryCommand enthält die Daten zum Erstellen einer Zeitbuchung
+type CreateTimeEntryCommand struct {
+	UserID             uuid.UUID
+	ProjectID          uuid.UUID
+	ActivityID         uuid.UUID
+	TaskID             *uuid.UUID
+	StartTime          time.Time
+	EndTime            time.Time
+	Description        string
+	BillablePercentage int
+}
+
+// CreateTimeEntryUseCase repräsentiert den Anwendungsfall zum Erstellen einer Zeitbuchung
+type CreateTimeEntryUseCase struct {
+	timeEntryRepo repositories.TimeEntryRepository
+	projectRepo   repositories.ProjectRepository
+	activityRepo  repositories.ActivityRepository
+	userRepo      repositories.UserRepository
+}
+
+// NewCreateTimeEntryUseCase erstellt eine neue Instanz des UseCase
+func NewCreateTimeEntryUseCase(
+	timeEntryRepo repositories.TimeEntryRepository,
+	projectRepo repositories.ProjectRepository,
+	activityRepo repositories.ActivityRepository,
+	userRepo repositories.UserRepository,
+) *CreateTimeEntryUseCase {
+	return &CreateTimeEntryUseCase{
+		timeEntryRepo: timeEntryRepo,
+		projectRepo:   projectRepo,
+		activityRepo:  activityRepo,
+		userRepo:      userRepo,
+	}
+}
+
+// Execute führt den Anwendungsfall aus
+func (uc *CreateTimeEntryUseCase) Execute(ctx context.Context, companyID uuid.UUID, cmd CreateTimeEntryCommand) functional.Result[*entities.TimeEntry] {
+	// Validierung
+	if err := validator.ValidateStruct(cmd); err != nil {
+		return functional.Failure[*entities.TimeEntry](err)
+	}
+
+	// Überprüfen, ob Projekt existiert und zum gleichen Tenant gehört
+	projectResult := uc.projectRepo.FindByID(ctx, companyID, cmd.ProjectID)
+	if projectResult.IsFailure() {
+		return functional.Failure[*entities.TimeEntry](projectResult.Error())
+	}
+
+	// Überprüfen, ob Activity existiert und zum gleichen Tenant gehört
+	activityResult := uc.activityRepo.FindByID(ctx, companyID, cmd.ActivityID)
+	if activityResult.IsFailure() {
+		return functional.Failure[*entities.TimeEntry](activityResult.Error())
+	}
+	activity := activityResult.Value()
+
+	// Benutzer abrufen für den Stundensatz
+	userResult := uc.userRepo.FindByID(ctx, companyID, cmd.UserID)
+	if userResult.IsFailure() {
+		return functional.Failure[*entities.TimeEntry](userResult.Error())
+	}
+	user := userResult.Value()
+
+	// Berechnung der Dauer in Minuten
+	durationMinutes := int(cmd.EndTime.Sub(cmd.StartTime).Minutes())
+
+	// TimeEntry erstellen
+	timeEntry := &entities.TimeEntry{
+		TenantEntity: entities.TenantEntity{
+			CompanyID: companyID,
+		},
+		UserID:             cmd.UserID,
+		ProjectID:          cmd.ProjectID,
+		ActivityID:         cmd.ActivityID,
+		TaskID:             cmd.TaskID,
+		StartTime:          cmd.StartTime,
+		EndTime:            cmd.EndTime,
+		DurationMinutes:    durationMinutes,
+		Description:        cmd.Description,
+		BillablePercentage: cmd.BillablePercentage,
+		BillingRate:        activity.BillingRate,
+	}
+
+	// Speichern der TimeEntry
+	return uc.timeEntryRepo.Create(ctx, timeEntry)
+}
diff --git a/docu/code_examples/gorm_entities.go b/docu/code_examples/gorm_entities.go
new file mode 100644
index 0000000..0ae6192
--- /dev/null
+++ b/docu/code_examples/gorm_entities.go
@@ -0,0 +1,104 @@
+package entities
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+)
+
+// BaseEntity enthält gemeinsame Felder für alle Entitäten
+type BaseEntity struct {
+	ID        uuid.UUID      `gorm:"type:uuid;primary_key"`
+	CreatedAt time.Time      `gorm:"autoCreateTime"`
+	UpdatedAt time.Time      `gorm:"autoUpdateTime"`
+	DeletedAt gorm.DeletedAt `gorm:"index"`
+}
+
+// BeforeCreate setzt eine neue UUID vor dem Erstellen
+func (base *BaseEntity) BeforeCreate(tx *gorm.DB) error {
+	if base.ID == uuid.Nil {
+		base.ID = uuid.New()
+	}
+	return nil
+}
+
+// TenantEntity erweitert BaseEntity um Company-ID für Multi-Tenancy
+type TenantEntity struct {
+	BaseEntity
+	CompanyID uuid.UUID `gorm:"type:uuid;index:idx_tenant"`
+}
+
+// Role repräsentiert eine Benutzerrolle
+type Role struct {
+	BaseEntity
+	Name        string `gorm:"unique;not null"`
+	Description string
+	Permissions []Permission `gorm:"many2many:role_permissions;"`
+}
+
+// Permission repräsentiert eine einzelne Berechtigung
+type Permission struct {
+	BaseEntity
+	Resource string `gorm:"not null"`
+	Action   string `gorm:"not null"`
+	UniqueID string `gorm:"uniqueIndex"`
+}
+
+// User repräsentiert einen Benutzer im System
+type User struct {
+	TenantEntity
+	Email        string `gorm:"uniqueIndex;not null"`
+	FirstName    string
+	LastName     string
+	PasswordHash string    `gorm:"not null"`
+	RoleID       uuid.UUID `gorm:"type:uuid"`
+	Role         Role      `gorm:"foreignKey:RoleID"`
+	HourlyRate   float64
+	IsActive     bool `gorm:"default:true"`
+}
+
+// FullName gibt den vollständigen Namen des Benutzers zurück
+func (u User) FullName() string {
+	return u.FirstName + " " + u.LastName
+}
+
+// TimeEntry repräsentiert eine Zeitbuchung
+type TimeEntry struct {
+	TenantEntity
+	UserID             uuid.UUID  `gorm:"type:uuid;index:idx_user"`
+	User               User       `gorm:"foreignKey:UserID"`
+	ProjectID          uuid.UUID  `gorm:"type:uuid;index:idx_project"`
+	Project            Project    `gorm:"foreignKey:ProjectID"`
+	ActivityID         uuid.UUID  `gorm:"type:uuid"`
+	Activity           Activity   `gorm:"foreignKey:ActivityID"`
+	TaskID             *uuid.UUID `gorm:"type:uuid;null"`
+	Task               *Task      `gorm:"foreignKey:TaskID"`
+	StartTime          time.Time  `gorm:"not null;index:idx_time_range"`
+	EndTime            time.Time  `gorm:"not null;index:idx_time_range"`
+	DurationMinutes    int        `gorm:"not null"`
+	Description        string
+	BillablePercentage int `gorm:"default:100"`
+	BillingRate        float64
+}
+
+type Project struct {
+	TenantEntity
+	Name string
+}
+
+type Activity struct {
+	TenantEntity
+	Name string
+}
+
+type Task struct {
+	TenantEntity
+	Name string
+}
+
+// CalculateBillableAmount berechnet den abrechenbaren Betrag
+func (t TimeEntry) CalculateBillableAmount() float64 {
+	hours := float64(t.DurationMinutes) / 60.0
+	return hours * t.BillingRate * (float64(t.BillablePercentage) / 100.0)
+}
diff --git a/docu/code_examples/react_component.tsx b/docu/code_examples/react_component.tsx
new file mode 100644
index 0000000..905f65f
--- /dev/null
+++ b/docu/code_examples/react_component.tsx
@@ -0,0 +1,136 @@
+// presentation/components/timeTracker/Timer/Timer.tsx
+import React, { useState, useEffect } from 'react';
+import { useTimeTracking } from '../../../hooks/useTimeTracking';
+import { pipe, Option, fromNullable } from '../../../../utils/fp/option';
+import { Button } from '../../common/Button';
+import { formatDuration } from '../../../../utils/date/dateUtils';
+
+interface TimerProps {
+    onComplete?: (duration: number) => void;
+}
+
+export const Timer: React.FC<TimerProps> = ({ onComplete }) => {
+    const [isRunning, setIsRunning] = useState(false);
+    const [startTime, setStartTime] = useState<Option<Date>>(Option.none());
+    const [elapsedTime, setElapsedTime] = useState(0);
+    const [selectedProject, setSelectedProject] = useState<Option<string>>(Option.none());
+    const [selectedActivity, setSelectedActivity] = useState<Option<string>>(Option.none());
+
+    const { lastTimeEntry, projects, activities } = useTimeTracking();
+
+    // Beim ersten Rendering die letzte Zeitbuchung laden
+    useEffect(() => {
+        pipe(
+            fromNullable(lastTimeEntry),
+            Option.map(entry => {
+                setSelectedProject(Option.some(entry.projectId));
+                setSelectedActivity(Option.some(entry.activityId));
+            })
+        );
+    }, [lastTimeEntry]);
+
+    // Timer-Logik
+    useEffect(() => {
+        let interval: NodeJS.Timeout | null = null;
+
+        if (isRunning) {
+            interval = setInterval(() => {
+                const now = new Date();
+                pipe(
+                    startTime,
+                    Option.map(start => {
+                        const diff = now.getTime() - start.getTime();
+                        setElapsedTime(Math.floor(diff / 1000));
+                    })
+                );
+            }, 1000);
+        } else if (interval) {
+            clearInterval(interval);
+        }
+
+        return () => {
+            if (interval) clearInterval(interval);
+        };
+    }, [isRunning, startTime]);
+
+    // Timer starten
+    const handleStart = () => {
+        setStartTime(Option.some(new Date()));
+        setIsRunning(true);
+    };
+
+    // Timer stoppen
+    const handleStop = () => {
+        setIsRunning(false);
+
+        // Prüfen, ob Projekt und Aktivität ausgewählt wurden
+        const projectId = pipe(
+            selectedProject,
+            Option.getOrElse(() => '')
+        );
+
+        const activityId = pipe(
+            selectedActivity,
+            Option.getOrElse(() => '')
+        );
+
+        if (projectId && activityId && onComplete) {
+            onComplete(elapsedTime);
+        }
+
+        // Timer zurücksetzen
+        setElapsedTime(0);
+        setStartTime(Option.none());
+    };
+
+    return (
+        <div className="bg-white rounded-lg shadow-md p-4">
+            <div className="text-4xl text-center font-mono mb-4">
+                {formatDuration(elapsedTime)}
+            </div>
+
+            <div className="grid grid-cols-2 gap-4 mb-4">
+                <div>
+                    <label className="block text-sm font-medium text-gray-700 mb-1">
+                        Projekt
+                    </label>
+                    <select
+                        className="w-full border border-gray-300 rounded-md px-3 py-2"
+                        value={pipe(selectedProject, Option.getOrElse(() => ''))}
+                        onChange={(e) => setSelectedProject(Option.some(e.target.value))}
+                        disabled={isRunning}
+                    >
+                        <option value="">Projekt auswählen</option>
+                        {projects.map((project) => (
+                            <option key={project.id} value={project.id}>
+                                {project.name}
+                            </option>
+                        ))}
+                    </select>
+                </div>
+
+                <div>
+                    <label className="block text-sm font-medium text-gray-700 mb-1">
+                        Tätigkeit
+                    </label>
+                    <select
+                        className="w-full border border-gray-300 rounded-md px-3 py-2"
+                        value={pipe(selectedActivity, Option.getOrElse(() => ''))}
+                        onChange={(e) => setSelectedActivity(Option.some(e.target.value))}
+                        disabled={isRunning}
+                    >
+                        <option value="">Tätigkeit auswählen</option>
+                        {activities.map((activity) => (
+                            <option key={activity.id} value={activity.id}>
+                                {activity.name}
+                            </option>
+                        ))}
+                    </select>
+                </div>
+            </div>
+
+            <div className="flex justify-center">
+            </div>
+        </div>
+    );
+};
\ No newline at end of file
diff --git a/docu/concept/files.md b/docu/concept/files.md
deleted file mode 100644
index fdb2919..0000000
--- a/docu/concept/files.md
+++ /dev/null
@@ -1,103 +0,0 @@
-timetracker-frontend/
-├── public/                     # Statische Dateien
-│   ├── assets/
-│   │   ├── images/
-│   │   ├── icons/
-│   │   └── fonts/
-│   └── locales/                # Mehrsprachige Inhalte
-│       ├── de/
-│       └── en/
-├── src/
-│   ├── app/                    # Next.js 13+ App Router
-│   │   ├── api/                # API-Routen (falls nötig)
-│   │   ├── (auth)/             # Authentifizierungsseiten
-│   │   │   ├── login/
-│   │   │   └── register/
-│   │   ├── dashboard/          # Dashboard-Seiten
-│   │   │   ├── page.tsx
-│   │   │   └── layout.tsx
-│   │   ├── time-tracking/      # Zeiterfassungsseiten
-│   │   │   ├── page.tsx
-│   │   │   ├── [id]/
-│   │   │   └── components/
-│   │   ├── projects/           # Projektseiten
-│   │   │   ├── page.tsx
-│   │   │   └── [id]/
-│   │   ├── customers/          # Kundenseiten
-│   │   │   ├── page.tsx
-│   │   │   └── [id]/
-│   │   ├── reports/            # Berichtsseiten
-│   │   │   ├── page.tsx
-│   │   │   └── [type]/
-│   │   ├── admin/              # Administrationsseiten
-│   │   │   ├── users/
-│   │   │   ├── companies/
-│   │   │   └── settings/
-│   │   ├── kanban/             # Kanban-Boards (Version 2)
-│   │   │   ├── page.tsx
-│   │   │   └── [id]/
-│   │   ├── layout.tsx
-│   │   └── page.tsx
-│   ├── components/             # Wiederverwendbare Komponenten
-│   │   ├── common/             # Allgemeine Komponenten
-│   │   │   ├── Button.tsx
-│   │   │   ├── Card.tsx
-│   │   │   ├── Input.tsx
-│   │   │   └── ...
-│   │   ├── layout/             # Layout-Komponenten
-│   │   │   ├── Navbar.tsx
-│   │   │   ├── Sidebar.tsx
-│   │   │   ├── Footer.tsx
-│   │   │   └── ...
-│   │   ├── dashboard/          # Dashboard-Komponenten
-│   │   │   ├── ActivityChart.tsx
-│   │   │   ├── RecentEntries.tsx
-│   │   │   └── ...
-│   │   ├── timetracker/        # Zeiterfassungskomponenten
-│   │   │   ├── Timer.tsx
-│   │   │   ├── EntryForm.tsx
-│   │   │   └── ...
-│   │   ├── reports/            # Berichtskomponenten
-│   │   │   ├── ReportFilter.tsx
-│   │   │   ├── Chart.tsx
-│   │   │   └── ...
-│   │   └── kanban/             # Kanban-Komponenten (Version 2)
-│   │       ├── Board.tsx
-│   │       ├── Column.tsx
-│   │       ├── Card.tsx
-│   │       └── ...
-│   ├── hooks/                  # Custom React Hooks
-│   │   ├── useAuth.ts
-│   │   ├── useTimeTracking.ts
-│   │   ├── useProjects.ts
-│   │   └── ...
-│   ├── lib/                    # Hilfsfunktionen und Bibliotheken
-│   │   ├── api.ts              # API Client
-│   │   ├── auth.ts             # Auth-Utilities
-│   │   ├── date-utils.ts       # Date-Helpers
-│   │   └── ...
-│   ├── types/                  # TypeScript-Typdefinitionen
-│   │   ├── auth.ts
-│   │   ├── user.ts
-│   │   ├── timeTracking.ts
-│   │   ├── project.ts
-│   │   └── ...
-│   ├── store/                  # State Management (falls benötigt)
-│   │   ├── slices/
-│   │   └── index.ts
-│   ├── styles/                 # CSS/SCSS Styles
-│   │   ├── globals.css
-│   │   └── theme.ts
-│   └── utils/                  # Allgemeine Hilfsfunktionen
-│       ├── format.ts
-│       ├── validation.ts
-│       └── ...
-├── .env.local.example
-├── .eslintrc.json
-├── next.config.js
-├── package.json
-├── tailwind.config.js
-├── tsconfig.json
-├── jest.config.js              # Test-Konfiguration
-├── postcss.config.js           # PostCSS-Konfiguration
-└── README.md
\ No newline at end of file
diff --git a/docu/database_schema.md b/docu/database_schema.md
new file mode 100644
index 0000000..2d45884
--- /dev/null
+++ b/docu/database_schema.md
@@ -0,0 +1,160 @@
+# Database Schema (PostgreSQL)
+
+```sql
+-- Multi-Tenant
+CREATE TABLE companies (
+    id UUID PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    address TEXT,
+    contact_email VARCHAR(255),
+    contact_phone VARCHAR(50),
+    logo_url TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Users and Roles
+CREATE TABLE roles (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(50) UNIQUE NOT NULL,
+    permissions JSONB
+);
+
+CREATE TABLE users (
+    id UUID PRIMARY KEY,
+    company_id UUID REFERENCES companies(id),
+    email VARCHAR(255) UNIQUE NOT NULL,
+    password_hash VARCHAR(255) NOT NULL,
+    first_name VARCHAR(100),
+    last_name VARCHAR(100),
+    role_id INTEGER REFERENCES roles(id),
+    hourly_rate DECIMAL(10, 2),
+    is_active BOOLEAN DEFAULT TRUE,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Customers
+CREATE TABLE customers (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(255) NOT NULL,
+    contact_person VARCHAR(255),
+    email VARCHAR(255),
+    phone VARCHAR(50),
+    address TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Projects
+CREATE TABLE projects (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    customer_id UUID REFERENCES customers(id),
+    name VARCHAR(255) NOT NULL,
+    description TEXT,
+    start_date DATE,
+    end_date DATE,
+    status VARCHAR(50),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Activities
+CREATE TABLE activities (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(255) NOT NULL,
+    description TEXT,
+    billing_rate DECIMAL(10, 2),
+    is_active BOOLEAN DEFAULT TRUE,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Time bookings
+CREATE TABLE time_entries (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    user_id UUID NOT NULL REFERENCES users(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    activity_id UUID NOT NULL REFERENCES activities(id),
+    start_time TIMESTAMP NOT NULL,
+    end_time TIMESTAMP NOT NULL,
+    duration INTEGER NOT NULL, -- in minutes
+    description TEXT,
+    billable_percentage INTEGER NOT NULL DEFAULT 100,
+    billing_rate DECIMAL(10, 2),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Version 2: Sprint/Task Management
+CREATE TABLE sprints (
+    id UUID PRIMARY KEY,
+    project_id UUID NOT NULL REFERENCES projects(id),
+    name VARCHAR(255) NOT NULL,
+    start_date DATE NOT NULL,
+    end_date DATE NOT NULL,
+    status VARCHAR(50),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE task_statuses (
+    id SERIAL PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(100) NOT NULL,
+    color VARCHAR(7),
+    position INTEGER NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE tasks (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    sprint_id UUID REFERENCES sprints(id),
+    title VARCHAR(255) NOT NULL,
+    description TEXT,
+    assignee_id UUID REFERENCES users(id),
+    status_id INTEGER REFERENCES task_statuses(id),
+    priority VARCHAR(50),
+    estimate INTEGER, -- in minutes
+    due_date TIMESTAMP,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE kanban_boards (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    name VARCHAR(255) NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE kanban_columns (
+    id UUID PRIMARY KEY,
+    board_id UUID NOT NULL REFERENCES kanban_boards(id),
+    name VARCHAR(100) NOT NULL,
+    position INTEGER NOT NULL,
+    task_status_id INTEGER REFERENCES task_statuses(id),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Linking time entries and tasks
+ALTER TABLE time_entries ADD COLUMN task_id UUID REFERENCES tasks(id);
+
+-- Indexes for performance
+CREATE INDEX idx_time_entries_user ON time_entries(user_id);
+CREATE INDEX idx_time_entries_project ON time_entries(project_id);
+CREATE INDEX idx_time_entries_date ON time_entries(start_time);
+CREATE INDEX idx_projects_company ON projects(company_id);
+CREATE INDEX idx_users_company ON users(company_id);
+CREATE INDEX idx_tasks_project ON tasks(project_id);
+CREATE INDEX idx_tasks_sprint ON tasks(sprint_id);
diff --git a/docu/deployment_devops.md b/docu/deployment_devops.md
new file mode 100644
index 0000000..c757f62
--- /dev/null
+++ b/docu/deployment_devops.md
@@ -0,0 +1,17 @@
+# Deployment and DevOps
+
+## Containerization
+- Docker containers for backend and frontend
+- Docker Compose for development environment
+- Kubernetes manifests for production environment
+
+## CI/CD Pipeline
+- Automated tests (Unit, Integration, E2E)
+- Automated deployment
+- Version management
+
+## Monitoring and Logging
+- Prometheus for metrics
+- Grafana for visualization
+- ELK Stack or similar for logging
+- Alerting for critical events
diff --git a/docu/concept/Readme.md b/docu/draft/concept/Readme.md
similarity index 100%
rename from docu/concept/Readme.md
rename to docu/draft/concept/Readme.md
diff --git a/docu/draft/concept/claude.md b/docu/draft/concept/claude.md
new file mode 100644
index 0000000..40a50ef
--- /dev/null
+++ b/docu/draft/concept/claude.md
@@ -0,0 +1,389 @@
+# Zeiterfassungstool - Projektstruktur
+
+## Backend (Go)
+
+```
+timetracker-backend/
+├── cmd/                        # Einstiegspunkte für die Anwendung
+│   ├── api/                    # API-Server
+│   │   └── main.go
+│   └── worker/                 # Hintergrundprozesse (Reports, Benachrichtigungen usw.)
+│       └── main.go
+├── internal/                   # Interner Code, nicht exportierbar
+│   ├── auth/                   # Authentifizierung und Autorisierung
+│   │   ├── jwt.go
+│   │   ├── middleware.go
+│   │   ├── permissions.go
+│   │   └── service.go
+│   ├── tenant/                 # Multi-Tenant-Funktionalität
+│   │   ├── middleware.go
+│   │   └── service.go
+│   ├── user/                   # Benutzerverwaltung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── company/                # Unternehmensverwaltung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── customer/               # Kundenverwaltung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── project/                # Projektverwaltung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── activity/               # Tätigkeitsverwaltung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── timetracking/           # Zeiterfassung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── billing/                # Abrechnung
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── reporting/              # Berichtswesen
+│   │   ├── generator.go
+│   │   ├── pdf.go
+│   │   └── service.go
+│   ├── notification/           # Benachrichtigungen
+│   │   ├── email.go
+│   │   ├── inapp.go
+│   │   └── service.go
+│   ├── kanban/                 # Kanban-Board (Version 2)
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── task/                   # Task-Management (Version 2)
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── sprint/                 # Sprint-Management (Version 2)
+│   │   ├── model.go
+│   │   ├── repository.go
+│   │   └── service.go
+│   ├── config/                 # Konfiguration
+│   │   └── config.go
+│   └── database/               # Datenbankzugriff
+│       ├── migrations/
+│       ├── seeds/
+│       └── connection.go
+├── pkg/                        # Öffentliche Pakete, die exportiert werden können
+│   ├── apierror/               # API-Fehlerobjekte
+│   │   └── error.go
+│   ├── logger/                 # Logging-Funktionalität
+│   │   └── logger.go
+│   ├── validator/              # Validierungsfunktionen
+│   │   └── validator.go
+│   └── utils/                  # Allgemeine Hilfsfunktionen
+│       ├── dates.go
+│       ├── encryption.go
+│       └── helpers.go
+├── api/                        # API-Definitionen
+│   ├── handlers/               # API-Handler
+│   │   ├── auth.go
+│   │   ├── user.go
+│   │   ├── company.go
+│   │   ├── customer.go
+│   │   ├── project.go
+│   │   ├── timetracking.go
+│   │   ├── reporting.go
+│   │   └── task.go
+│   ├── middleware/             # API-Middleware
+│   │   ├── auth.go
+│   │   ├── tenant.go
+│   │   └── logging.go
+│   ├── routes/                 # API-Routen
+│   │   └── routes.go
+│   └── swagger/                # Swagger-Dokumentation
+│       └── swagger.yaml
+├── test/                       # Tests
+│   ├── integration/
+│   ├── unit/
+│   └── mocks/
+├── scripts/                    # Skripte für Build, Deployment usw.
+│   ├── build.sh
+│   ├── migrate.sh
+│   └── seed.sh
+├── docker/                     # Docker-Konfiguration
+│   ├── Dockerfile
+│   └── docker-compose.yml
+├── go.mod
+├── go.sum
+├── .env.example
+└── README.md
+```
+
+## Frontend (NextJS)
+
+```
+timetracker-frontend/
+├── public/                     # Statische Dateien
+│   ├── assets/
+│   │   ├── images/
+│   │   ├── icons/
+│   │   └── fonts/
+│   └── locales/                # Mehrsprachige Inhalte
+│       ├── de/
+│       └── en/
+├── src/
+│   ├── app/                    # Next.js 13+ App Router
+│   │   ├── api/                # API-Routen (falls nötig)
+│   │   ├── (auth)/             # Authentifizierungsseiten
+│   │   │   ├── login/
+│   │   │   └── register/
+│   │   ├── dashboard/          # Dashboard-Seiten
+│   │   │   ├── page.tsx
+│   │   │   └── layout.tsx
+│   │   ├── time-tracking/      # Zeiterfassungsseiten
+│   │   │   ├── page.tsx
+│   │   │   ├── [id]/
+│   │   │   └── components/
+│   │   ├── projects/           # Projektseiten
+│   │   │   ├── page.tsx
+│   │   │   └── [id]/
+│   │   ├── customers/          # Kundenseiten
+│   │   │   ├── page.tsx
+│   │   │   └── [id]/
+│   │   ├── reports/            # Berichtsseiten
+│   │   │   ├── page.tsx
+│   │   │   └── [type]/
+│   │   ├── admin/              # Administrationsseiten
+│   │   │   ├── users/
+│   │   │   ├── companies/
+│   │   │   └── settings/
+│   │   ├── kanban/             # Kanban-Boards (Version 2)
+│   │   │   ├── page.tsx
+│   │   │   └── [id]/
+│   │   ├── layout.tsx
+│   │   └── page.tsx
+│   ├── components/             # Wiederverwendbare Komponenten
+│   │   ├── common/             # Allgemeine Komponenten
+│   │   │   ├── Button.tsx
+│   │   │   ├── Card.tsx
+│   │   │   ├── Input.tsx
+│   │   │   └── ...
+│   │   ├── layout/             # Layout-Komponenten
+│   │   │   ├── Navbar.tsx
+│   │   │   ├── Sidebar.tsx
+│   │   │   ├── Footer.tsx
+│   │   │   └── ...
+│   │   ├── dashboard/          # Dashboard-Komponenten
+│   │   │   ├── ActivityChart.tsx
+│   │   │   ├── RecentEntries.tsx
+│   │   │   └── ...
+│   │   ├── timetracker/        # Zeiterfassungskomponenten
+│   │   │   ├── Timer.tsx
+│   │   │   ├── EntryForm.tsx
+│   │   │   └── ...
+│   │   ├── reports/            # Berichtskomponenten
+│   │   │   ├── ReportFilter.tsx
+│   │   │   ├── Chart.tsx
+│   │   │   └── ...
+│   │   └── kanban/             # Kanban-Komponenten (Version 2)
+│   │       ├── Board.tsx
+│   │       ├── Column.tsx
+│   │       ├── Card.tsx
+│   │       └── ...
+│   ├── hooks/                  # Custom React Hooks
+│   │   ├── useAuth.ts
+│   │   ├── useTimeTracking.ts
+│   │   ├── useProjects.ts
+│   │   └── ...
+│   ├── lib/                    # Hilfsfunktionen und Bibliotheken
+│   │   ├── api.ts              # API Client
+│   │   ├── auth.ts             # Auth-Utilities
+│   │   ├── date-utils.ts       # Date-Helpers
+│   │   └── ...
+│   ├── types/                  # TypeScript-Typdefinitionen
+│   │   ├── auth.ts
+│   │   ├── user.ts
+│   │   ├── timeTracking.ts
+│   │   ├── project.ts
+│   │   └── ...
+│   ├── store/                  # State Management (falls benötigt)
+│   │   ├── slices/
+│   │   └── index.ts
+│   ├── styles/                 # CSS/SCSS Styles
+│   │   ├── globals.css
+│   │   └── theme.ts
+│   └── utils/                  # Allgemeine Hilfsfunktionen
+│       ├── format.ts
+│       ├── validation.ts
+│       └── ...
+├── .env.local.example
+├── .eslintrc.json
+├── next.config.js
+├── package.json
+├── tailwind.config.js
+├── tsconfig.json
+├── jest.config.js              # Test-Konfiguration
+├── postcss.config.js           # PostCSS-Konfiguration
+└── README.md
+```
+
+## Datenbankschema (PostgreSQL)
+
+```sql
+-- Multi-Tenant
+CREATE TABLE companies (
+    id UUID PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    address TEXT,
+    contact_email VARCHAR(255),
+    contact_phone VARCHAR(50),
+    logo_url TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Benutzer und Rollen
+CREATE TABLE roles (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(50) UNIQUE NOT NULL,
+    permissions JSONB
+);
+
+CREATE TABLE users (
+    id UUID PRIMARY KEY,
+    company_id UUID REFERENCES companies(id),
+    email VARCHAR(255) UNIQUE NOT NULL,
+    password_hash VARCHAR(255) NOT NULL,
+    first_name VARCHAR(100),
+    last_name VARCHAR(100),
+    role_id INTEGER REFERENCES roles(id),
+    hourly_rate DECIMAL(10, 2),
+    is_active BOOLEAN DEFAULT TRUE,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Kunden
+CREATE TABLE customers (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(255) NOT NULL,
+    contact_person VARCHAR(255),
+    email VARCHAR(255),
+    phone VARCHAR(50),
+    address TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Projekte
+CREATE TABLE projects (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    customer_id UUID REFERENCES customers(id),
+    name VARCHAR(255) NOT NULL,
+    description TEXT,
+    start_date DATE,
+    end_date DATE,
+    status VARCHAR(50),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Tätigkeiten
+CREATE TABLE activities (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(255) NOT NULL,
+    description TEXT,
+    billing_rate DECIMAL(10, 2),
+    is_active BOOLEAN DEFAULT TRUE,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Zeitbuchungen
+CREATE TABLE time_entries (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    user_id UUID NOT NULL REFERENCES users(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    activity_id UUID NOT NULL REFERENCES activities(id),
+    start_time TIMESTAMP NOT NULL,
+    end_time TIMESTAMP NOT NULL,
+    duration INTEGER NOT NULL, -- in minutes
+    description TEXT,
+    billable_percentage INTEGER NOT NULL DEFAULT 100,
+    billing_rate DECIMAL(10, 2),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Version 2: Sprint/Task Management
+CREATE TABLE sprints (
+    id UUID PRIMARY KEY,
+    project_id UUID NOT NULL REFERENCES projects(id),
+    name VARCHAR(255) NOT NULL,
+    start_date DATE NOT NULL,
+    end_date DATE NOT NULL,
+    status VARCHAR(50),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE task_statuses (
+    id SERIAL PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    name VARCHAR(100) NOT NULL,
+    color VARCHAR(7),
+    position INTEGER NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE tasks (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    sprint_id UUID REFERENCES sprints(id),
+    title VARCHAR(255) NOT NULL,
+    description TEXT,
+    assignee_id UUID REFERENCES users(id),
+    status_id INTEGER REFERENCES task_statuses(id),
+    priority VARCHAR(50),
+    estimate INTEGER, -- in minutes
+    due_date TIMESTAMP,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE kanban_boards (
+    id UUID PRIMARY KEY,
+    company_id UUID NOT NULL REFERENCES companies(id),
+    project_id UUID NOT NULL REFERENCES projects(id),
+    name VARCHAR(255) NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE kanban_columns (
+    id UUID PRIMARY KEY,
+    board_id UUID NOT NULL REFERENCES kanban_boards(id),
+    name VARCHAR(100) NOT NULL,
+    position INTEGER NOT NULL,
+    task_status_id INTEGER REFERENCES task_statuses(id),
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Verknüpfung zwischen Zeitbuchungen und Tasks
+ALTER TABLE time_entries ADD COLUMN task_id UUID REFERENCES tasks(id);
+
+-- Indizes für Performance
+CREATE INDEX idx_time_entries_user ON time_entries(user_id);
+CREATE INDEX idx_time_entries_project ON time_entries(project_id);
+CREATE INDEX idx_time_entries_date ON time_entries(start_time);
+CREATE INDEX idx_projects_company ON projects(company_id);
+CREATE INDEX idx_users_company ON users(company_id);
+CREATE INDEX idx_tasks_project ON tasks(project_id);
+CREATE INDEX idx_tasks_sprint ON tasks(sprint_id);
+```
\ No newline at end of file
diff --git a/docu/concept/structure.md b/docu/draft/concept/structure.md
similarity index 100%
rename from docu/concept/structure.md
rename to docu/draft/concept/structure.md
diff --git a/docu/extensibility_integrations.md b/docu/extensibility_integrations.md
new file mode 100644
index 0000000..3f761c4
--- /dev/null
+++ b/docu/extensibility_integrations.md
@@ -0,0 +1,6 @@
+# Extensibility and Integrations
+
+- API for external billing systems and calendar integration
+- Single Sign-On (Google, Microsoft, SAML)
+- Plugin system and custom fields for extensibility
+- Analytics and BI export
diff --git a/docu/frontend_architecture.md b/docu/frontend_architecture.md
new file mode 100644
index 0000000..ea52051
--- /dev/null
+++ b/docu/frontend_architecture.md
@@ -0,0 +1,102 @@
+# Frontend Architecture (Next.js)
+
+**Note:** This document describes a *conceptual* architecture and is not a final, binding requirement.
+
+The frontend uses **Next.js** with **TypeScript** and **FPTS** for functional programming.
+
+## Project Structure
+
+```
+timetracker-frontend/
+├── public/                         # Statische Dateien
+│   ├── assets/
+│   └── locales/                    # i18n Übersetzungen
+├── src/
+│   ├── app/                        # Next.js App Router
+│   │   ├── api/                    # API Routes
+│   │   ├── (auth)/                 # Auth Pages
+│   │   ├── dashboard/
+│   │   ├── time-tracking/
+│   │   ├── projects/
+│   │   └── ...
+│   ├── domain/                     # Domain Model (analog zu Backend)
+│   │   ├── entities/               # Domain Entities
+│   │   │   ├── user.ts
+│   │   │   ├── timeEntry.ts
+│   │   │   ├── project.ts
+│   │   │   └── ...
+│   │   └── valueObjects/           # Value Objects
+│   │       ├── money.ts
+│   │       ├── duration.ts
+│   │       └── ...
+│   ├── application/                # Anwendungsfälle
+│   │   ├── auth/                   # Auth Use Cases
+│   │   ├── timeTracking/           # Time Tracking Use Cases
+│   │   ├── projects/               # Projects Use Cases
+│   │   └── ...
+│   ├── infrastructure/             # Infrastruktur
+│   │   ├── api/                    # API Client
+│   │   │   ├── apiClient.ts        # Axios Konfiguration
+│   │   │   ├── endpoints.ts        # API Endpunkte
+│   │   │   └── interceptors.ts     # Request/Response Interceptors
+│   │   ├── storage/                # Lokale Speicherung
+│   │   │   ├── localStorage.ts
+│   │   │   └── sessionStorage.ts
+│   │   └── external/               # Externe Dienste
+│   │       └── ...
+│   ├── presentation/               # Präsentationsschicht
+│   │   ├── components/             # UI Komponenten
+│   │   │   ├── common/             # Allgemeine Komponenten
+│   │   │   │   ├── Button/
+│   │   │   │   ├── Card/
+│   │   │   │   └── ...
+│   │   │   ├── layout/             # Layout Komponenten
+│   │   │   │   ├── Navbar/
+│   │   │   │   ├── Sidebar/
+│   │   │   │   └── ...
+│   │   │   ├── timeTracker/        # Zeiterfassung Komponenten
+│   │   │   │   ├── Timer/
+│   │   │   │   ├── EntryForm/
+│   │   │   │   └── ...
+│   │   │   └── ...
+│   │   ├── hooks/                  # Custom React Hooks
+│   │   │   ├── useAuth.ts
+│   │   │   ├── useTimeTracking.ts
+│   │   │   └── ...
+│   │   ├── providers/              # Context Provider
+│   │   │   ├── AuthProvider.tsx
+│   │   │   ├── ThemeProvider.tsx
+│   │   │   └── ...
+│   │   └── pages/                  # Page Components (für App Router)
+│   │       ├── DashboardPage.tsx
+│   │       ├── TimeTrackingPage.tsx
+│   │       └── ...
+│   ├── utils/                      # Utilities
+│   │   ├── fp/                     # Funktionale Programmierung (FPTS)
+│   │   │   ├── option.ts
+│   │   │   ├── result.ts
+│   │   │   └── ...
+│   │   ├── date/                   # Datumsfunktionen
+│   │   │   └── dateUtils.ts
+│   │   ├── formatting/             # Formattierung
+│   │   │   ├── numberFormat.ts
+│   │   │   └── ...
+│   │   └── validation/             # Validierung
+│   │       └── validators.ts
+│   ├── types/                      # TypeScript Typendefinitionen
+│   │   ├── api.ts                  # API Response/Request Typen
+│   │   ├── auth.ts                 # Auth Typen
+│   │   └── ...
+│   └── styles/                     # Globale Styles
+│       ├── globals.css
+│       └── theme.ts
+├── docu/                           # Frontend-spezifische Dokumentation
+│   ├── component_library.md
+│   ├── state_management.md
+│   └── ...
+├── next.config.js
+├── tailwind.config.js
+├── tsconfig.json
+├── package.json
+└── README.md
+```
diff --git a/docu/general_overview.md b/docu/general_overview.md
new file mode 100644
index 0000000..e310848
--- /dev/null
+++ b/docu/general_overview.md
@@ -0,0 +1,40 @@
+# General Overview
+
+## Technology Stack
+
+### Backend
+- Go with fp-go
+- PostgreSQL with ORM (GORM or Bun)
+- Swagger/OpenAPI
+- JWT-based Authentication
+
+### Frontend
+- Next.js with fp-ts
+- React and Tailwind CSS
+- Responsive Webdesign
+- Progressive Web App (PWA)
+
+## Multi-Tenancy & Roles
+- **Multi-Tenancy**: Isolation of data per company (tenant).
+- **Roles**: Admin, Company-Admin, Manager, Auditor, User.
+
+## Data Models
+- **Company** (Tenant)
+- **User** (with roles, hourly rate)
+- **Customer**
+- **Project** (with customer reference)
+- **Activity** (billing rate)
+- **Booking** (time, user, project, activity, optional description, billability 0-100%)
+
+## Functional Requirements
+### Version 1
+- Master data management (customers, projects, activities, users)
+- Time tracking with start/stop function and parameter inheritance from the last booking
+- Clear dashboard with recent bookings and tracker
+- Aggregated reports by period, project, customer, employee with PDF export
+- Graphical dashboards (diagrams)
+
+### Version 2
+- Project management with sprints, tasks
+- Kanban boards for task management
+- Direct linking of tasks with time bookings
diff --git a/docu/llm_guidance.md b/docu/llm_guidance.md
new file mode 100644
index 0000000..070d71e
--- /dev/null
+++ b/docu/llm_guidance.md
@@ -0,0 +1,92 @@
+# LLM Guidance for the Time Tracking Project
+
+This document provides guidance for Large Language Models (LLMs) working on the Time Tracking and Management System.
+
+## File Locations
+
+Here's a guide to finding information within the project:
+
+**Documentation:**
+
+-   **General Project Overview:** `docu/general_overview.md`
+-   **Backend Architecture (Go):** `docu/backend_architecture.md`
+-   **Frontend Architecture (Next.js):** `docu/frontend_architecture.md`
+-   **Database Schema (PostgreSQL):** `docu/database_schema.md`
+-   **Deployment and DevOps:** `docu/deployment_devops.md`
+-   **Security and Privacy:** `docu/security_privacy.md`
+-   **Extensibility and Integrations:** `docu/extensibility_integrations.md`
+- **This LLM Guidance Document:** `docu/llm_guidance.md`
+-   **Top Level Documentation Index:** `docu/README.md`
+
+**Code (Conceptual - see architecture documents for details):**
+
+-   **Backend (Go):**  (Refer to `docu/backend_architecture.md` for the conceptual structure.  Actual code structure may differ.)
+    -   **Conceptual File Locations:**
+        -   `backend-go/internal/domain/entities/`: Core domain entities (User, Company, Project, etc.)
+        -   `backend-go/internal/domain/repositories/`: Interfaces for data access.
+        -   `backend-go/internal/domain/services/`: Business logic implementation.
+        -   `backend-go/internal/infrastructure/persistence/`: Database interactions (GORM).
+        -   `backend-go/internal/interfaces/http/handlers/`: API endpoint handlers.
+        -   `backend-go/internal/interfaces/http/middleware/`: Authentication and tenant isolation middleware.
+    -   **Code Examples:**
+        -   `docu/code_examples/gorm_entities.go`: Example GORM entity definitions.
+        -   `docu/code_examples/fpgo_repository.go`: Example FPGO repository interface.
+        -   `docu/code_examples/fpgo_service.go`: Example FPGO service implementation.
+        -   `docu/code_examples/api_handler.go`: Example API handler.
+
+-   **Frontend (Next.js):** (Refer to `docu/frontend_architecture.md` for the conceptual structure. Actual code structure may differ.)
+    -   **Conceptual File Locations:**
+        -   `frontend-nextjs/pages/`:  Application pages.
+        -   `frontend-nextjs/components/`: Reusable UI components.
+        -   `frontend-nextjs/lib/`:  API interaction and helper functions.
+        -   `frontend-nextjs/types/`: TypeScript type definitions.
+    -  **Code Examples:**
+        - `docu/code_examples/react_component.tsx`: Example React component.
+
+**Important Note about Code Examples:** The files in `docu/code_examples/` are for illustrative purposes *only*. They do *not* represent a runnable project structure.  Treat each file as an isolated example.  The package declarations within these files (e.g., `package entities`, `package repositories`, `package main`) are conceptual and should be interpreted in the context of the described architecture, *not* as a literal directory structure.  Do not attempt to run `go get` or similar commands based on these examples, as the necessary project structure and dependencies are not present.
+
+## Rules and Guidelines
+
+1.  **Clean Architecture:** Adhere to Clean Architecture principles. Separate business logic (domain) from infrastructure concerns (database, UI).
+2.  **Domain-Driven Design (DDD):**  Use DDD concepts to model the domain accurately.
+3.  **Multi-Tenancy:** Ensure all operations are scoped to the correct tenant (company). Use the `company_id` for data isolation.
+4.  **FPGO and FPTS:**  Favor functional programming paradigms in both Go (FPGO) and TypeScript (FPTS).
+5.  **Modularity:**  Keep code modular and well-organized.
+6.  **Error Handling:** Implement robust error handling and validation.
+7.  **Security:** Prioritize security.  Use JWT for authentication and RBAC for authorization.  Sanitize inputs to prevent injection attacks.
+8.  **Testing:** Write unit and integration tests for all new code.
+9. **Documentation**: Keep the documentation up to date.
+10. **Conceptual Architecture**: The architecture files are a *concept*, not a final implementation.
+
+## Ideas to Follow
+
+-   **Small, Focused Modules:**  Break down tasks into small, well-defined modules.
+-   **Descriptive Naming:** Use clear and descriptive names for variables, functions, and files.
+-   **Comments:**  Add comments to explain complex logic.
+-   **Consistency:** Maintain consistent coding style and patterns.
+-   **Leverage Libraries:** Use existing libraries (FPGO, FPTS, GORM, Gin, Axios, etc.) where appropriate.
+- **Ask for Clarification:** If unsure about any aspect of the project, use the `ask_followup_question` tool.
+- **Visually Appealing Design:** (Especially for Claude models) Strive for a visually appealing and user-friendly interface. Consider using appropriate colors, layout, and components.
+- **Prefer Replacements:** When making changes to existing files, favor the `replace_in_file` tool over `write_to_file` to minimize context usage and cost. Only use `write_to_file` for creating new files or making extensive, non-localized changes.
+
+## Workflow for Limited Context
+
+If you encounter context limitations or are instructed to work in smaller chunks, follow this workflow:
+
+1.  **Request a Summary:** If needed, ask for a brief summary of the current task and relevant file content.
+2.  **Plan in Chunks:** Divide the task into smaller, manageable sub-tasks.
+3.  **Focus on One Chunk:** Work on one sub-task at a time.
+4.  **Use `replace_in_file`:** Make targeted changes using `replace_in_file`.
+5.  **Iterate:** Repeat steps 3 and 4 for each sub-task.
+6.  **Provide Context Briefing:** When moving to a new chunk or file, provide a concise summary of the previous work and the current objective. This helps maintain context across multiple interactions.
+
+## Code Organization and Style
+
+- **Functional File Division:** Divide functionalities logically into separate files. This improves readability, maintainability, and helps manage context size.
+- **Code Reusability:** Design code to be reusable and extensible. Anticipate future requirements and create components or functions that can be adapted for different purposes.
+- **Common Sense:** Apply general good coding practices, even if they seem obvious. This includes things like:
+    - Using meaningful variable and function names.
+    - Adding comments to explain non-obvious logic.
+    - Handling edge cases and potential errors.
+    - Keeping functions and components concise and focused.
+    - Following consistent indentation and formatting.
diff --git a/docu/security_privacy.md b/docu/security_privacy.md
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+# Security and Data Privacy
+
+- Tenant isolation
+- TLS encryption and encrypted storage of sensitive data
+- Audit logs (comprehensive logging)
+- GDPR compliant (data export, right to be forgotten)