One thing I miss about Canada is coffee houses. (means something different in German btw) There was one near where I lived, and you could bring your guitar or other instrument and each person would get about 15 minutes to play, and it was a ton of fun. Is there anything of this nature in Hamburg?
Another thing I did a little was called a song circle. A group of music enthusiasts would get together either in a private home, or a public place where we were welcome. Then you form a circle and each person takes a turn. If you are a musician you play a song. If you are not a musician, you can either perform a poem, tell a joke, or request that one of the musicians plays a song. Also a lot of fun. Perhaps there are folks (no pun with folk music intended) who would be interested in trying this?