Я увидел много ответ для этому вопросу, а ничто совершенно.(Это грамматика хорошая?)
Everyone gives answers avoiding the topic of cases. From what I've gathered, "учу" is correct, but the case of "русский" changes the meaning from 'learn' to 'teach'? "Учусь" means teach myself, right, which is pretty much the same as "learn" if no ones else is teaching you. I could use some elaboration on this.