@Pierre572, the lack of housing is not due to a lack of construction workers. On this classified ads site alone, there are +7000 construction workers actively looking for work today.
Neither it is due to the 0,6% of the housing market that is being offered as short term rentals.
It is due to a lack of political will, and an overwhelmingly slow bureaucratic process that makes it impossible for private individuals or small businesses to even build a garden shed. So building is a luxury only reserved for big corporations who can afford a costly permit application, which takes months, if not years to process (partly also due to a huge lack of personnel in the Bauamt).
On the other hand, any born and bred Berliner can tell you the government owns thousands of sqm in abandoned real estate. E.g. Das Haus der Statistik alone, comprises 50.000 sqm in the heart of the city, and is abandoned since the '90. It could easily house 1600 people. So this property alone equals 12% of all the "illegal" entire apartment rentals on AirBnB! You can see many more examples here.
@Helen3, I agree with you that social housing must be protected.
I personally know of couples who are both on welfare, have each a paid-for apartment (by welfare), but live at only one of the partner/spouse's house. The apartment of the other is simply empty during the whole year. Offering it as a short term lease is not even an option, because of its illegality paired by a pathologic fear of reprisal from the welfare office. And to give it up? "Why? It is "for free" and I will never find another apartment like this...".
This not-so-rare a recipe means 2 unemployed + . govt pays for 2 social housing, 1 of which is empty year round.
On the other hand, were this unemployed person allowed to start a small short term rental, then you would have -1 person less on welfare, and -1 social housing less for the govt. to pick up the bill for.
In both cases, the number of available free living spaces stays the same.
I am fortunate enough to say I never had to claim a single cent nor welfare benefits myslef. If I did, and were to be living on social housing, I would not try to get into short term rentals either, as it would mean way too much risk. I am thus confident my co-hosts are mostly not on welfare either, but quite the contrary, trying to stay away from it. So if the silly efforts of the Senate were to succeed, that would mean the government will create +26000 more unemployed, +26000 more people on welfare , -26000 less available social housing units.
