This is a great flat in a very convenient location. It is (relatively) recently built, so contemporary rather than historic in any way. It was spotlessly clean. The mattresses are very comfortable (foam, as I recall); the bedding is as you would expect in Germany, i.e., of good quality. The weather was chilly when we were there so we didn't sit on the balcony but having the open view from the balcony onto the trees outside was a real pleasure. It makes the flat seem very spacious. Check-in at the Hotel Midi desk in the building was easy as was leaving luggage with them on the day we departed in the evening (ignore the leaflet in the flat which implies you have to take it to a luggage deposit shop- I assume it says this as this flat is offered on numerous online rental platforms).
It's ten minutes, five tram stops from the Central train station, near the Tegel Airport bus (which you can get on/off one stop before/after the Hauptbanhof at Invalidenpark when it is empty and before the crowds pack the bus at the station). It is a short walk to Rosenthaler Platz U-bahn station and a 25 minute walk to the Museum Island. So unless you need to be in a specific other part of Berlin, this is very convenient and central.
The neighbourhood is residential, upmarket and filled with families as the building sits right on the small Volkspark am Weinberg, a small urban park space used by locals. The neighbourhood has many cafes and restaurants. On the ground floor of the building is a Vietnamese restaurant which was excellent and very good value for the daily specials. The food was a step above some of the other Vietnamese restaurants on the adjoining main roads.
I would definitely stay here again without hesitation.