Non-Germans want to learn German and want to take part in social life.
Germans are not as enthusiastic yet. They don`t want to feel obligated.

How can we still create social interaction?

That´s what we already tried out;)

IDEA AFTER RESEARCH:

Giving German people a SIGN which could be a print on a shirt, sticker, bag, what ever that says: “Hey, join us!”/”Don´t be shy!”/”Take part!”…
They´ll have the opportunity to put it on in a situation where they want foreign people to participate – Non-Germans wouldn´t have a as hard time to bring oneselfes to do the first step.