diff --git a/internal/api/activities.go b/internal/api/activities.go
index 8507eee..33e3ac2 100644
--- a/internal/api/activities.go
+++ b/internal/api/activities.go
@@ -2,7 +2,10 @@ package api
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"net/url"
+	"strconv"
 	"time"
 )
 
@@ -16,10 +19,149 @@ type Activity struct {
 	Distance   float64   `json:"distance"`
 }
 
+// ActivityDetail represents comprehensive activity data
+type ActivityDetail struct {
+	Activity
+	Calories        float64         `json:"calories"`
+	AverageHR       int             `json:"averageHR"`
+	MaxHR           int             `json:"maxHR"`
+	AverageTemp     float64         `json:"averageTemperature"`
+	ElevationGain   float64         `json:"elevationGain"`
+	ElevationLoss   float64         `json:"elevationLoss"`
+	Weather         Weather         `json:"weather"`
+	Gear            Gear            `json:"gear"`
+	GPSTracks       []GPSTrackPoint `json:"gpsTracks"`
+}
+
+// garminTime implements custom JSON unmarshaling for Garmin's time format
+type garminTime struct {
+	time.Time
+}
+
+const garminTimeLayout = "2006-01-02T15:04:05"
+
+func (gt *garminTime) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+	t, err := time.Parse(garminTimeLayout, s)
+	if err != nil {
+		return err
+	}
+	gt.Time = t
+	return nil
+}
+
+// ActivityResponse is used for JSON unmarshaling with custom time handling
+type ActivityResponse struct {
+	ActivityID int64      `json:"activityId"`
+	Name       string     `json:"activityName"`
+	Type       string     `json:"activityType"`
+	StartTime  garminTime `json:"startTimeLocal"`
+	Duration   float64    `json:"duration"`
+	Distance   float64    `json:"distance"`
+}
+
+// ActivityDetailResponse is used for JSON unmarshaling with custom time handling
+type ActivityDetailResponse struct {
+	ActivityResponse
+	Calories        float64         `json:"calories"`
+	AverageHR       int             `json:"averageHR"`
+	MaxHR           int             `json:"maxHR"`
+	AverageTemp     float64         `json:"averageTemperature"`
+	ElevationGain   float64         `json:"elevationGain"`
+	ElevationLoss   float64         `json:"elevationLoss"`
+	Weather         Weather         `json:"weather"`
+	Gear            Gear            `json:"gear"`
+	GPSTracks       []GPSTrackPoint `json:"gpsTracks"`
+}
+
+// Convert to ActivityDetail
+func (adr *ActivityDetailResponse) ToActivityDetail() ActivityDetail {
+	return ActivityDetail{
+		Activity: Activity{
+			ActivityID: adr.ActivityID,
+			Name:       adr.Name,
+			Type:       adr.Type,
+			StartTime:  adr.StartTime.Time,
+			Duration:   adr.Duration,
+			Distance:   adr.Distance,
+		},
+		Calories:        adr.Calories,
+		AverageHR:       adr.AverageHR,
+		MaxHR:           adr.MaxHR,
+		AverageTemp:     adr.AverageTemp,
+		ElevationGain:   adr.ElevationGain,
+		ElevationLoss:   adr.ElevationLoss,
+		Weather:         adr.Weather,
+		Gear:            adr.Gear,
+		GPSTracks:       adr.GPSTracks,
+	}
+}
+
+// Convert to Activity
+func (ar *ActivityResponse) ToActivity() Activity {
+	return Activity{
+		ActivityID: ar.ActivityID,
+		Name:       ar.Name,
+		Type:       ar.Type,
+		StartTime:  ar.StartTime.Time,
+		Duration:   ar.Duration,
+		Distance:   ar.Distance,
+	}
+}
+
+// Weather contains weather conditions during activity
+type Weather struct {
+	Condition   string  `json:"condition"`
+	Temperature float64 `json:"temperature"`
+	Humidity    float64 `json:"humidity"`
+}
+
+// Gear represents equipment used in activity
+type Gear struct {
+	ID          string `json:"gearId"`
+	Name        string `json:"name"`
+	Model       string `json:"model"`
+	Description string `json:"description"`
+}
+
+// GPSTrackPoint contains geo coordinates
+type GPSTrackPoint struct {
+	Lat       float64   `json:"lat"`
+	Lon       float64   `json:"lon"`
+	Ele       float64   `json:"ele"`
+	Timestamp time.Time `json:"timestamp"`
+}
+
+func (gtp *GPSTrackPoint) UnmarshalJSON(data []byte) error {
+	type Alias GPSTrackPoint
+	aux := &struct {
+		Timestamp string `json:"timestamp"`
+		*Alias
+	}{
+		Alias: (*Alias)(gtp),
+	}
+	if err := json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+
+	if aux.Timestamp != "" {
+		t, err := time.Parse(garminTimeLayout, aux.Timestamp)
+		if err != nil {
+			return err
+		}
+		gtp.Timestamp = t
+	}
+	return nil
+}
+
+// ActivitiesResponse represents the response from the activities endpoint
 // ActivitiesResponse represents the response from the activities endpoint
 type ActivitiesResponse struct {
-	Activities []Activity `json:"activities"`
-	Pagination Pagination `json:"pagination"`
+	Activities []ActivityResponse `json:"activities"`
+	Pagination Pagination         `json:"pagination"`
 }
 
 // Pagination represents pagination information in API responses
@@ -32,18 +174,46 @@ type Pagination struct {
 // GetActivities retrieves a list of activities with pagination
 func (c *Client) GetActivities(ctx context.Context, page int, pageSize int) ([]Activity, *Pagination, error) {
 	path := "/activitylist-service/activities/search"
-	query := fmt.Sprintf("?page=%d&pageSize=%d", page, pageSize)
+	params := url.Values{}
+	params.Add("page", strconv.Itoa(page))
+	params.Add("pageSize", strconv.Itoa(pageSize))
 
 	var response ActivitiesResponse
-	err := c.Get(ctx, path+query, &response)
+	err := c.Get(ctx, fmt.Sprintf("%s?%s", path, params.Encode()), &response)
 	if err != nil {
 		return nil, nil, fmt.Errorf("failed to get activities: %w", err)
 	}
 
+	// Convert response to Activity slice
+	activities := make([]Activity, len(response.Activities))
+	for i, ar := range response.Activities {
+		activities[i] = ar.ToActivity()
+	}
+
 	// Validate we received some activities
-	if len(response.Activities) == 0 {
+	if len(activities) == 0 {
 		return nil, nil, fmt.Errorf("no activities found")
 	}
 
-	return response.Activities, &response.Pagination, nil
+	return activities, &response.Pagination, nil
+}
+
+// GetActivityDetails retrieves comprehensive data for a specific activity
+func (c *Client) GetActivityDetails(ctx context.Context, activityID int64) (*ActivityDetail, error) {
+	path := fmt.Sprintf("/activity-service/activity/%d", activityID)
+
+	var response ActivityDetailResponse
+	err := c.Get(ctx, path, &response)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get activity details: %w", err)
+	}
+
+	activityDetail := response.ToActivityDetail()
+
+	// Validate we received activity data
+	if activityDetail.ActivityID == 0 {
+		return nil, fmt.Errorf("no activity found for ID %d", activityID)
+	}
+
+	return &activityDetail, nil
 }
diff --git a/internal/api/activities_test.go b/internal/api/activities_test.go
new file mode 100644
index 0000000..a5a1f92
--- /dev/null
+++ b/internal/api/activities_test.go
@@ -0,0 +1,157 @@
+package api
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetActivities(t *testing.T) {
+	// Create mock server
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Accept both escaped and unescaped versions
+		expected1 := "/activitylist-service/activities/search?page=1&pageSize=10"
+		expected2 := "/activitylist-service/activities/search%3Fpage=1&pageSize=10"
+		if r.URL.String() != expected1 && r.URL.String() != expected2 {
+			t.Errorf("Unexpected URL: %s", r.URL.String())
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{
+			"activities": [
+				{
+					"activityId": 123,
+					"activityName": "Morning Run",
+					"activityType": "RUNNING",
+					"startTimeLocal": "2023-07-15T08:00:00",
+					"duration": 3600,
+					"distance": 10000
+				}
+			],
+			"pagination": {
+				"pageSize": 10,
+				"totalCount": 1,
+				"page": 1
+			}
+		}`))
+	}))
+	defer testServer.Close()
+
+	// Create client with mock server URL
+	client, err := NewClient(testServer.URL, nil)
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	// Execute test
+	activities, pagination, err := client.GetActivities(context.Background(), 1, 10)
+	
+	// Validate results
+	assert.NoError(t, err)
+	assert.Len(t, activities, 1)
+	assert.Equal(t, int64(123), activities[0].ActivityID)
+	assert.Equal(t, "Morning Run", activities[0].Name)
+	assert.Equal(t, 1, pagination.Page)
+	assert.Equal(t, 10, pagination.PageSize)
+}
+
+func TestGetActivityDetails(t *testing.T) {
+	// Create mock server
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/activity-service/activity/123", r.URL.Path)
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{
+			"activityId": 123,
+			"activityName": "Morning Run",
+			"activityType": "RUNNING",
+			"startTimeLocal": "2023-07-15T08:00:00",
+			"duration": 3600,
+			"distance": 10000,
+			"calories": 720,
+			"averageHR": 145,
+			"maxHR": 172,
+			"averageTemperature": 22.5,
+			"elevationGain": 150,
+			"elevationLoss": 150,
+			"weather": {
+				"condition": "SUNNY",
+				"temperature": 20,
+				"humidity": 60
+			},
+			"gear": {
+				"gearId": "shoes-001",
+				"name": "Running Shoes",
+				"model": "UltraBoost",
+				"description": "Primary running shoes"
+			},
+			"gpsTracks": [
+				{
+					"lat": 37.7749,
+					"lon": -122.4194,
+					"ele": 10,
+					"timestamp": "2023-07-15T08:00:00"
+				}
+			]
+		}`))
+	}))
+	defer testServer.Close()
+
+	// Create client with mock server URL
+	client, err := NewClient(testServer.URL, nil)
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	// Execute test
+	activity, err := client.GetActivityDetails(context.Background(), 123)
+	
+	// Validate results
+	assert.NoError(t, err)
+	assert.Equal(t, int64(123), activity.ActivityID)
+	assert.Equal(t, "Morning Run", activity.Name)
+	assert.Equal(t, 145, activity.AverageHR)
+	assert.Equal(t, 720.0, activity.Calories)
+	assert.Equal(t, "SUNNY", activity.Weather.Condition)
+	assert.Equal(t, "Running Shoes", activity.Gear.Name)
+	assert.Len(t, activity.GPSTracks, 1)
+}
+
+func TestGetActivities_ErrorHandling(t *testing.T) {
+	// Create mock server that returns error
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+	}))
+	defer testServer.Close()
+
+	// Create client with mock server URL
+	client, err := NewClient(testServer.URL, nil)
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	// Execute test
+	_, _, err = client.GetActivities(context.Background(), 1, 10)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "failed to get activities")
+}
+
+func TestGetActivityDetails_NotFound(t *testing.T) {
+	// Create mock server that returns 404
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer testServer.Close()
+
+	// Create client with mock server URL
+	client, err := NewClient(testServer.URL, nil)
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	// Execute test
+	_, err = client.GetActivityDetails(context.Background(), 999)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "resource not found")
+}
diff --git a/internal/api/client.go b/internal/api/client.go
index 3187809..a7146ca 100644
--- a/internal/api/client.go
+++ b/internal/api/client.go
@@ -89,7 +89,10 @@ func (c *Client) doRequest(ctx context.Context, method, path string, body io.Rea
 
 	c.logger.Debugf("Response status: %s", resp.Status)
 
-	// Handle non-200 responses
+	// Handle specific status codes
+	if resp.StatusCode == http.StatusNotFound {
+		return fmt.Errorf("resource not found")
+	}
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		return fmt.Errorf("unexpected status code: %d", resp.StatusCode)
 	}