The apartment is really pretty, clean and comfortable. It's in a relatively good location, right next to an S Bahn station and a tram station which is just a few stops from Alexanderplatz. It's also next to a 24 hour supermarket.

The couple prepared a fool-proof and very helpful itinerary with various attractions, bars, clubs, cafes, etc to check out as well.
The slight downside is that the door is a bit hard to open so you do struggle with it somewhat.

Also remember to bring your own toiletries such as soap. Just a heads up: note that there is a late check-in fee of 20 EUR which I had to pay because my arrival was delayed as my ICE train into Berlin was cancelled. It did get a bit noisy at times as the apartment is on the street level but it's nothing ear plugs can't fix.