Unable to answer "What kind of service building is this?" – Translator Tower (Service Building) – https://osm.org/way/362332786 via StreetComplete_ee 61.1:

There is a tower with lots of Antennae nearby. Seems to be some kind of telecommunication building, but probably not for connecting landlines.

Attached photo(s):
https://streetcomplete.app/p/319873.jpg