We did not meet Rainer, but he responded quickly to messages, as did Nicola who welcomed us when we arrived and was very responsive to any queries we had! Although not that central, Neukölln is a great neighbourhood and the apartment is minutes away from the S+U Bahn, so it's easy to travel elsewhere in the city relatively quickly. Neukölln itself is a fantastic area though, being so close to the Tempelhofer Feld and with lots of bars and cafes close by.