Katharina and Peter's apartment was conveniently located, clean, and very well equipped.
Peter who welcomed us when we arrived at West Bahnhof was extremely kind. He even picked us up from the station since my friend and I were stupidly lost when the apartment was only few walks from there and he helped us with our heavy luggage. And he let us to leave our luggage until 14:45 later that day so that we don't have to carry our bags around after checking out.
We had a wonderful time there at the apartment and I guarantee you will.