I rented this room at Basem's place for 21 days and couldn't have been happier. Basem is a super nice guy who will try to make your life as easy as possible and the accommodation is perfect. It's a big room with lots of space and the entire apartment is very clean. I could use the kitchen to cook which was very convenient and in general Basem was always very accommodating of all my requests.
Moreover, the apartment is located in a really quiet local neighborhood (when I say quiet I really mean it, you can hear absolutely no noise during most of the time), only 1 minute away from a nice supermarket and 10 minutes away from kurfürstendamm and its many good restaurants.
If you need a place to stay in Berlin this is a no-brainer, I really recommend it!