After you complete a course and don't turn on review mode, it disappears from your Home.
If you turn on review mode, it will show up in your Home again when the course becomes ready for study.
You can see all your courses in "My Courses." (Swipe the screen to the right in your Home → Tap My Courses)
Also to turn on/off review mode for each completed course, tap a course title and "Turn on/off review mode".