Sylvia is a great host and the apartment is very nice. It is not far from the airport. We took a taxi, but there is a once-per-hour direct bus connection as well.
Check in was easy, Sylvia welcomed us to the apartment and showed us around. She even had arranged toys and books for our son. Sylvia had also placed a helpful guide in one of the drawers, which we discovered a little late.
The apartment is clean and spacious. It was made by combining two studio apartments, so you get two kitchens, beds, toilets, and balconies.
The apartment is a little far from the centre. There is an S-Bahn stop 15 mins walks away (or a 5 mins bus ride). The S-Bahn takes you to Potsdamerplatz in 25 mins.
There is a grocery store (Lidl) and a bakery near the apartment. A few mins walk takes you to the main shopping area of Lichtenrade, which has many restaurants, cafes, and stores.
Overall it is a nice, quiet place to stay.