how do i get past level 15
i have mastered all of the skills through level 15. how do i get to the next level?
The only way to do that is through translations, skill tree practice and vocabulary practice.
But honestly, I think that Duolingo is really lacking at the level you have reached, and doesn't really help you anything. Doing translations might be helpful, but there is barely any feedback for them at the high levels.
I also think that this is something that Duolingo badly needs to fix, because the way it works now the users who reach a high level and can translate the difficult stuff doesn't get anything in return and would be better served in their language learning doing other things.