So I finished Spanish level 12--got a congratulatory note from Duo, and voila--no more levels?? Can't find 'em anyway. So sad, cuz I'm not close to being fluent.
Duo's maximum level is 25 but completing the tree won't bring you there. It also either a lot of review or immersion.
Also, Duolingo won't make you fluent. It just teaches the basics of a language...