This building has been extended to all the way in the back, there is no backyard anymore.

The image at https://warnochwas.de/index.php/s/x7ZsJgJkDHTm8XG explains it better (that is supposed to be a straight line).

The front part (the currently mapped building) consists of three floors plus a rooftop flat, the back part (not currently mapped) is only on the ground floor.