You can **** in facebook for groups like "Neu in (city)" or to speak german search for "Tandem (city)" to find people who are looking for a tandem partner.
You can also check on couchsurfing.org for local events, they usually have weekly meetups in bigger cities...
there is this website called meetup.*** where you can find local events as well
If you tell us where you live we can give you more advice =)