diff --git a/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/activity/[activityid]/page.tsx b/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/activity/[activityid]/page.tsx
index 937cfd27..1ba17cb3 100644
--- a/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/activity/[activityid]/page.tsx
+++ b/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/activity/[activityid]/page.tsx
@@ -11,8 +11,8 @@ import { getCourse } from "@services/courses/courses";
 import VideoActivity from "@components/ActivityViews/Video/Video";
 import useSWR, { mutate } from "swr";
 import { Check } from "lucide-react";
-import { maskActivityAsComplete } from "@services/courses/activity";
 import { swrFetcher } from "@services/utils/requests";
+import { markActivityAsComplete } from "@services/courses/activity";
 
 function ActivityPage(params: any) {
   const activityid = params.params.activityid;
@@ -20,12 +20,11 @@ function ActivityPage(params: any) {
   const orgslug = params.params.orgslug;
 
   const { data: course, error: error_course } = useSWR(`${getAPIUrl()}courses/meta/course_${courseid}`, swrFetcher);
-  const { data: activity, error: error_activity } = useSWR(`${getAPIUrl()}activities/activity_${activityid}`, swrFetcher);
+  const { data: activity, error: error_activity } = useSWR(`${getAPIUrl()}trail/org_slug/${orgslug}/trail`, swrFetcher);
 
-  console.log(course, activity);
 
   async function markActivityAsCompleteFront() {
-    const activity = await maskActivityAsComplete("" + activityid, courseid, activity.activity_id.replace("activity_", ""));
+    const trail = await markActivityAsComplete(orgslug, courseid, activityid);
     mutate(`${getAPIUrl()}activities/activity_${activityid}`);
     mutate(`${getAPIUrl()}courses/meta/course_${courseid}`);
   }
@@ -76,9 +75,10 @@ function ActivityPage(params: any) {
               {activity.type == "video" && <VideoActivity course={course} activity={activity} />}
 
               <ActivityMarkerWrapper>
-                {course.activity.activities_marked_complete &&
-                course.activity.activities_marked_complete.includes("activity_" + activityid) &&
-                course.activity.status == "ongoing" ? (
+                
+                {course.trail.activities_marked_complete &&
+                course.trail.activities_marked_complete.includes("activity_" + activityid) &&
+                course.trail.status == "ongoing" ? (
                   <button style={{ backgroundColor: "green" }}>
                     <i>
                       <Check size={20}></Check>
diff --git a/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/page.tsx b/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/page.tsx
index 41103208..0f2f3b4c 100644
--- a/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/page.tsx
+++ b/front/app/_orgs/[orgslug]/(withmenu)/course/[courseid]/page.tsx
@@ -23,7 +23,6 @@ const CourseIdPage = (params: any) => {
 
   async function quitCourse() {
 
-
     // Close activity
     let activity = await removeCourse("course_" + courseid,  orgslug);
     console.log(activity);
diff --git a/front/services/courses/activity.ts b/front/services/courses/activity.ts
index ea3802d1..d2fcda94 100644
--- a/front/services/courses/activity.ts
+++ b/front/services/courses/activity.ts
@@ -7,21 +7,21 @@ import { getAPIUrl } from "@services/config/config";
 */
 
 export async function startCourse(course_id: string, org_slug: string) {
-  const result: any = await fetch(`${getAPIUrl()}trail/${org_slug}/add_course/${course_id}`, RequestBody("POST", null))
+  const result: any = await fetch(`${getAPIUrl()}trail/org_slug/${org_slug}/add_course/${course_id}`, RequestBody("POST", null))
     .then((result) => result.json())
     .catch((error) => console.log("error", error));
   return result;
 }
 
 export async function removeCourse(course_id: string, org_slug: string) {
-  const result: any = await fetch(`${getAPIUrl()}trail/${org_slug}/remove_course/${course_id}`, RequestBody("POST", null))
+  const result: any = await fetch(`${getAPIUrl()}trail/org_slug/${org_slug}/remove_course/${course_id}`, RequestBody("POST", null))
     .then((result) => result.json())
     .catch((error) => console.log("error", error));
   return result;
 }
 
-export async function maskActivityAsComplete(org_id: string, course_id: string, activity_id: string) {
-  const result: any = await fetch(`${getAPIUrl()}activity/${org_id}/add_activity/${course_id}/${activity_id}`, RequestBody("POST", null))
+export async function markActivityAsComplete(org_slug: string, course_id: string, activity_id: string) {
+  const result: any = await fetch(`${getAPIUrl()}trail/org_slug/${org_slug}/add_activity/course_id/${course_id}/activity_id/${activity_id}`, RequestBody("POST", null))
     .then((result) => result.json())
     .catch((error) => console.log("error", error));
   return result;
diff --git a/src/routers/trail.py b/src/routers/trail.py
index ef345895..13b19fdd 100644
--- a/src/routers/trail.py
+++ b/src/routers/trail.py
@@ -30,8 +30,10 @@ async def api_get_trail_by_orgslug(request: Request, org_slug: str, user=Depends
     """
     return await get_user_trail_with_orgslug(request, user, org_slug=org_slug)
 
+# Courses in trail
 
-@router.post("/{org_slug}/add_course/{course_id}")
+
+@router.post("/org_slug/{org_slug}/add_course/{course_id}")
 async def api_add_course_to_trail(request: Request,  course_id: str, org_slug: str,   user=Depends(get_current_user)):
     """
     Add Course to trail
@@ -39,9 +41,17 @@ async def api_add_course_to_trail(request: Request,  course_id: str, org_slug: s
     return await add_course_to_trail(request, user,   org_slug, course_id)
 
 
-@router.post("/{org_slug}/remove_course/{course_id}")
+@router.post("/org_slug/{org_slug}/remove_course/{course_id}")
 async def api_remove_course_to_trail(request: Request,  course_id: str, org_slug: str,   user=Depends(get_current_user)):
     """
     Remove Course from trail
     """
     return await remove_course_from_trail(request, user,   org_slug, course_id)
+
+
+@router.post("/org_slug/{org_slug}/add_activity/course_id/{course_id}/activity_id/{activity_id}")
+async def api_add_activity_to_trail(request: Request, activity_id: str, course_id: str, org_slug: str,   user=Depends(get_current_user)):
+    """
+    Add Course to trail
+    """
+    return await add_activity_to_trail(request, user, course_id, org_slug, activity_id)
diff --git a/src/services/trail.py b/src/services/trail.py
index 69d74b34..ee71c870 100644
--- a/src/services/trail.py
+++ b/src/services/trail.py
@@ -130,18 +130,41 @@ async def get_user_trail_with_orgslug(request: Request, user: PublicUser, org_sl
     return Trail(**trail)
 
 
-async def add_activity_to_trail(request: Request, user: PublicUser, trail_id: str, course_id: str, activity_id: str) -> Trail:
+async def add_activity_to_trail(request: Request, user: PublicUser,  course_id: str, org_slug: str, activity_id: str) -> Trail:
     trails = request.app.db["trails"]
-    trail = await trails.find_one({"trail_id": trail_id, "user_id": user.user_id})
+    orgs = request.app.db["organizations"]
+    courseid = "course_" + course_id
+    activityid = "activity_" + activity_id
+
+    # get org_id from orgslug
+    org = await orgs.find_one({"slug": org_slug})
+    org_id = org["org_id"]
+   
+    
+    # find a trail with the user_id and course_id in the courses array 
+    trail = await trails.find_one({"user_id": user.user_id, "courses.course_id": courseid , "org_id": org_id})
+    
     if not trail:
         raise HTTPException(
             status_code=status.HTTP_404_NOT_FOUND, detail="Trail not found")
+    
+    # if a trail has course_id in the courses array, then add the activity_id to the activities_marked_complete array
     for element in trail["courses"]:
-        if element["course_id"] == course_id:
-            if activity_id not in element["activities_marked_complete"]:
-                element["activities_marked_complete"].append(activity_id)
-            break
-    await trails.replace_one({"trail_id": trail_id}, trail)
+        if element["course_id"] == courseid:
+            if "activities_marked_complete" in element:
+
+                # check if activity_id is already in the array
+                if activityid not in element["activities_marked_complete"]:
+                    element["activities_marked_complete"].append(activityid)
+                else: 
+                    raise HTTPException(
+                        status_code=status.HTTP_400_BAD_REQUEST, detail="Activity already marked complete")
+            else:
+                element["activities_marked_complete"] = [activity_id]
+    
+    # modify trail object 
+    await trails.replace_one({"trail_id": trail["trail_id"]}, trail)
+
     return Trail(**trail)
 
 
@@ -164,7 +187,6 @@ async def add_course_to_trail(request: Request, user: PublicUser, orgslug: str,
             status_code=status.HTTP_404_NOT_FOUND, detail="Trail not found")
 
     # check if course is already present in the trail
-
     for element in trail["courses"]:
         if element["course_id"] == course_id:
             raise HTTPException(