A rental contract may not contain anything that contradicts the law. Rental law is binding law. There are, among other things, legal rules for the notice period, the maximum rental price, additional costs and maintenance obligations. Please note, therefore, that provisions in the contract that contradict this are not valid. You are therefore not obliged to abide by them, even if you have signed the contract. Of course it is better to start by removing these kind of provisions from the contract. Then the landlord also knows where he stands.