Someone who was not the real owner of the apartment (presumably thief/criminal) put the place up on AirBnB. You unknowingly rented the place from this person, and during your stay, the real owner showed up and asked what you were doing in his house?
Someone who was not the real owner of the apartment (presumably thief/criminal) put the place up on AirBnB. You unknowingly rented the place from this person, and during your stay, the real owner showed up and asked what you were doing in his house?
From when I lived in Berlin it seemed subletting rental apartments wasn't uncommon. Subletting where you live has been common practice in Germany for a long time predating the rise of AirBnB, etc. Typically on classified ad sites or through specialist agencies. I've seen stores like yours before from a few years back discussed on toytown (an expat forum for people living in germany), so it's not just an AirBnB thing.
In practice, most Berlin landlords won't ever notice their flat being occasionally sublet to tourists by the tenant, but they will probably not be too happy when they notice.