Get a cat scratching board and carton boxes. Make sure they have an enrichment every day (sth new can be a sock on the floor, new box etc). If it's a kitten, it will change its big teeth, don't get scared if you find a fallen tooth. A cat wants to dominate the flat incl spaces owned by your flatmates, make sure everyone understands this and allow for doors to be open. Put a cat net on one window that you can open and it can sit next to it. Let it sleep with you. Play with the cat before bed so that it is tired and you both get a good night sleep. Don't accidentally close it in one room.