Fred is a very welcoming, funny, cool and open-minded host living in a art-deco style flat decorated with taste by his own, big, luminous, comfortable.
It is well located in Kreuzberg, a living district in the middle of Berlin. The town centre is very accessible by bus next door or S-Bahn with 5 minutes walking.
My friend and I really enjoyed our stay into Fred's flat (and Fred is a very good host) that I would highly recommand in Berlin.