This is a great place. It's a little hard to tell from the photos, but it has two bedrooms - one with a queen-sized bed, and one with two twin beds. It also has two couches in the living area that can be used for sleeping. It is in the attic and it's very charming and well done. It is also in a neighborhood with some history, and is a 5 minute walk to a summer palace that is open to the public and worth spending an hour or two.
The neighborhood is quiet, but it should be noted that it is in the flight path of a regional airport. There is a lot of airplane traffic, but it didn't bother us. And there are no planes between 23:00 and 7:00.
It is about a 15 - 20 minute walk to the S-Bahn. Bus stops are about 5 minutes closer, as are some restaurants and shops. From the S-Bahn, it is about 5 stops to central Berlin.
Ines is a great host. She even pre-stocked the refrigerator with a couple bottles of sparkling water and some fresh apples. If you are going to spend some time in Berlin, I would highly recommend this flat!