"You learn how to speak Vietnamese."
Translation:Bạn học nói tiếng Việt.
No way it is correct. Your sentence is translated as "How do you learn to speak Vietnamese?".
You put như thế nào at the end of the sentence and it turns to a question.
In my opinion, 'You learn to speak Vietnamese' (without how) should also work...
It sounds unnatural. If you want to say that way, the right sentence is Bạn học làm sao để nói tiếng Việt. But people rarely say like that.