Me like an immigrant of Germany, it was a very big target, to learn German perfectly - it took many years;
but as I began to study and did travel through Germany, too,
I made a discovery:
There are too many dialects in Germany, and all people think, that their dialect is the true one, and that the official German, you learn in the school, is a dialect, too.
So, the German you learn in Hannover is a different one, you learn in Bavaria;
also, when you are a teacher from the south Germany, and you go to middel Germany, to teach German, you will realize, that the school mates laugh at you - so you go back to your home south Germany, because you begin to feel like an alien in the another region of Germany;
so, please, tell me, what is the real idea behind "speak German", when the most Germans do not like to speak the official German?!


I think it would be nearly impossible for someone to learn German as a second language and be indistinguishable despite which regional dialect and or accent you try and adopt.