I think definitely offline. I mean learning online has some advantages, like you can learn whenever you want, you dont have like that "pressure" of going into a class. But if you are in a "real" class you can always ask questions right away.
Definitely German, I've been listening music in this language for a long time now, but I've never really had time to start learning (at least online). It seems quite difficult but it seems such a powerful language.