Thank you for your explanation, when creating notes always keep in mind to give as much information as possible 👍

This specific issue is actually completely unrelated to the OpenStreetMap or any other application using its data. The problem is that the Wikidata entry of the "Stadthalle Braunschweig" (used by Wikipedia and OsmAnd when using the offline Wikipedia feature) contains coordinates linked to this location right here, as this was the location of the old Stadthalle (see also https://de.wikipedia.org/wiki/Stadthalle_Braunschweig). This is obviously wrong nowadays, but not connected to OSM, though I will still fix this issue...