If you fixed "learnt" to the infinitive "learn", then both are syntactically possible, but for "If you don't speak your native language", you'd also need to change "would you learn it", which then doesn't work, to use another auxiliary verb such as "could", "can" or "will".
But neither expression makes much sense, because a native language is one that you grew up speaking, so you would have already learned it, by definition. You could substitute the name of another language, "Chinese", say and then your sentences would be more plausible.