Nicor
Unable to answer "What is the house number of this building?" for https://www.openstreetmap.org/way/511315502 via StreetComplete 3.2:

Das sind tatsächlich 2 Häuser mit den Nummern 9/9a und 10/10a

Attached photo(s):
https://lut.im/R5Cp0Gt0RH/gEjlT9Sq1bAfDmyr