To unenroll from a course:
1) Click on the ellipses at the top right-hand of the course player.
2) Click Unenroll from course.

https://www.google.com/search?q=udemy+how+to+leave+a+course&rlz=1C1GCEB_enIN936IN937&sxsrf=ALeKk01bTTuHDrR6AcWbtYCGblFMEsSF7g:1625998949038&tbm=isch&source=iu&ictx=1&fir=9SKFXKSGXruLQM%252CoosPxabTRDpOpM%252C_&vet=1&usg=AI4_-kRBSSqLo0ORxlLdi2OfU183VICF9g&sa=X&ved=2ahUKEwjSsIyO5trxAhVczjgGHa25DNwQ9QF6BAgIEAE#imgrc=9SKFXKSGXruLQM  - Help Link