Unable to answer "What kind of building is this?" – https://osm.org/way/497981426 via StreetComplete 57.1:

Vereinsheim des Modellflugvereins Fuchstal (www.mrv-fuchstal.de)

Attached photo(s):
https://westnordost.de/p/211269.jpg
https://westnordost.de/p/211270.jpg