Need more vocabulary practice
I'm learning Ukrainian, and I think that more emphasis on vocabulary would be helpful. While grammar comes easily to me, I often forget vocabulary if I don't study it by itself.
I think that users should be able to decide how much vocabulary they want to include. There could be a sort of scale, 1-5. 1 being emphasis on vocabulary and 5 grammar, with the rest falling in the middle.
Sometimes I do think that there should be more vocabulary from older lessons. If you're a person that tries to keep the whole tree golden, you'll learn vocab a lot because the skills don't stay gold for very long so you would need to practice that skill/those skills everyday