what can i do ?
30 years ago you could threaten him with sending a gang of Russian tough guys to his place. Today it doesn` work anymore. hahaha
So, you can go to court but that will cost you time and probably some money too if you decide to hire a lawyer. However, if he loses the case, the lawyer costs will be refunded to you.
he also wrote in my contract that everything was fine so i left the apartment and gave him the keys that day.
The court will certainly take this entry into a serious consideration.