Helpful host, nice area, all was well.
Tip: Should trains not be running to Grunewald for some reason, you can take the M19 bus from the S-Bahn station which runs east as far as the junction with Yorckstrasse and Mehringdamn. There is an underground station just north of here, or you can get off a little before at Yorckstrasse station. You can take a train to the city centre from both stations. If returning on the M19 late in the evening, make sure to get on one that is going to Grunewald station and not the one terminating somewhere else in Grunewald, although it's a short walk back to a bus stop on the route you should be on. Note: buses may suddenly terminate enroute but don't worry, there'll another along very soon