Not German so I can only talk about how it is going in another country:

- Massive change in the average household size: way fewer people live together now (delayed couple & family formation, divorce, etc.). If you go from 4 people per household to 2 people per household, now you need twice as many homes.

- Massive internal migration: declining population in a lot of rural areas and increasing in cities & their suburbs. So lot of empty houses and super cheap houses in Dumbfuck, Nowhere but scarce & expensive homes where people want to live.

Yes.

There is also the problem of housing "lost" to the lifestyles of the well-to-do - whether that's 1%'ers who own multiple houses, or regular housing which becomes short-term rentals (Airbnb or whatever). In places, those are major problems. Overall - the biggest problem those cause might be that they're socially divisive distractions from bigger issues.

Makes me think of the typical example where building more wider highways increases congestion because more people travel by car.