How many semesters?
How many semesters does the Russian course cover? Just one? Two? Three?
I think this is a question without a real answer. There are things which would, I hope, be covered in the first semester of any university course, but which you won't learn from duolingo. An obvious one would how to read and write. With pen and paper, I mean, not keyboard and screen. But there are other things in the course which wouldn't be covered until later semesters. So I don't think a numerical answer is really meaningful here.