I can't say anything about forcing people to sell flats (sounds contrived) but it's 100% possible to restrict ownership of many pets in standard rentral contracts. It is not possible to restrict small or quiet pets like a hamster, goldfish etc. but dogs, parrots etc. - sure. Cats are a grey area.
And your landlord can certainly terminate the contract if you keep a parrot in the flat without approval.
Actually they can never force you to sell, the 'landlord' can in theory get the lease cancelled so the property reverts to him. It will only happen if ground rents / service charges remain unpaid.
Cats are classed wild animals in the UK, the cat can actually chooses where to live! If you stop feeding one very quickly they will find a neighbour that will in the UK.
I had a very fat cat who got fed by everyone as he would stand by their fridges & cry!
Switzerland repeatedly has the highest standard of living in Surveys, the people who write those survey have never lived in CH. They can't imagine that in a well off society people only get a wash day maybe every 2 weeks.
In Germany everyone has their own washing machines in a room in the basement, works much better than the 'Swiss way'.
Pretty much everyone I know in France even if they live in tiny studio apartments have a washing machine in the bathroom.
I can do the laundry any day, almost any time, here in Switzerland, with shared infrastructure. Why? Good relations with neighbours, independent of the written rules (which also exist).
In Germany - well, no, not everyone has their own washing machine.
Indeed, we are all agreed that although we are not allowed to wash on a Sunday, you can book the rooms. Also, if emergancies occur (wetting the bed etc) that leeway is given about the 9pm shut off or sharing a slot.
Of course we have a sign-up system rather than an imposed one, and we don't have a locked laundry/mashine.
His behaviour is certainly not ok, but why don't you ask your roommate to teach you a few useful sentences in German, to see how he will react if you explain the situation in his language?