The place is just as described: the studio is quite large. Four of us fit comfortably. The double bed is not the most comfortable to sleep on with two people, but it was fine for a couple of days. Charlotte met us upon our arrival and had great tips about places to eat, etc in the neighborhood.
The neighborhood was a little seedy. It didn’t feel unsafe, but it’s very dirty and the main square near the apartment is quite crowded with people drinking. However, there were a number of good restaurants and cafes right near the apartment. And, it was very close to a metro stop, which made it very easy to get all over town. Berlin is such a huge city there’s really no way to stay near everything. It’s not walking distance to any of the big tourist attractions, but for the price it’s worth the ride on the very navigable metro.
Short version: there are probably nicer neighborhoods in the city. But it was affordable, quiet and easy to get to and from for our family’s 4 days in Berlin.