[helge5]

I _think_ those things are disconnected. If you stay more than 6 month + 1 days in Germany, I think it becomes your primary tax country and you fall into the German social system (for good or bad). But really, just guesswork. Ask someone :-)

If you are contracting for multiple clients, you should probably be cool. The thing which is problematic is if you only work for a single client (the mentioned "Scheinselbstständigkeit" - your claim to be self employed, but you really aren't). In this case Germany really just wants that you are regularly employed by that client company. (the reason is that this was commonly abused to force cheap labour into self employments, so that the employers also don't have to pay gov insurances and work around a whole lot of other laws ...)