What do 20 year olds like to do in Berlin?

Dear Berliners from Germany an elsewhere,

A good friend from Latin America has just informed me that his 20 year old son will be coming to Berlin next month for 2 weeks for a German intensive course. He will be pretty busy during the week with his German classes and is staying with a German host family but my friend has asked me if I could show him something on the weekend. Unfortunately, I have absolutely no idea what 20 year olds would enjoy. Can someone help me out with some inspiration please? Thanks a lot in advance and happy weekend everyone!