I see people asking about learning more advanced versions of the language. It seems like it has a lot already. I'm just curious, what kind of stuff does DuoLingo not cover?
As far as I know and can predict, Duolingo gives a basic language level which comprises about 2500-3000 words and basic grammar concepts. This should be enough to proceed from learning language to using it and sharpening it on practice. You'll get this level provided that you really understand all the grammar that is necessary to do all the exercises. I can't say if it is possible if you use ONLY Duolingo, because I use other resources, too.