Speaking as someone who lives in Germany, this is a common sentiment from old timey Germans that hasn’t been true for awhile. It’s far more than a week every year and it’ll only get worse.
It’s like the memory of the past is so strong it overwrites the present day experience. I think the truth of the matter is home ownership is so low that installing AC is never even considered by the owning class. Germans definitely have a culture of not needing AC and like superstitiously not liking them, but honestly California had similar beliefs when I lived there but they had just started to cave to the present reality. I think Germany is a decade behind on this matter and in 10 years 80% of the population will have AC and the last 20% will be the people whose landlords refuse to invest in their properties and blame it on the infrastructure not being built for AC.
I’d be curious why it’s impossible to set up a mini-split in your bedroom. That seems… Illogical. They are surface mounted pretty much anywhere externally, require a small hole to be drilled for the fluid exchange, and the mini split can fit inside any room on the wall or ceiling. Power shouldn’t be a problem either as that’s easy to wire through the same hole as the fluid exchange if need be.
Idk, I’m not an installer but the tech seems like you could make it work on a barn in the country or in the non-sensical backrooms - it’s not very demanding.