The current market still suffers from other forms of government regulation. The Mietendeckel still exists in some form via the Mietenspiegel, and basically the entire city under what Americans understand as rent-control.

How does it suffer to make it illegal to charge 10% more or less than the average for comparable housing? It seems to make it more stable and less volatile.

Go look up the Mietenspiegel price for your flat in your neighborhood, then pop open Immoscout and try and find one for that price.

Price controls = supply shortages. Basic principal of market economics.

But how does the market suffer from that? It implies that the Mietenspiegel is a bad policy. It only protects from price gauging or price dumping. If you are living in Berlin I would highly recommend looking up if you're paying too much.

Lines of 50 people to see an apartment sounds like a huge waste of man hours, which cost money to economy. This waste also grows quadratically: more people searching for longer.