Landlord is imposing me illegal rules as part of his contract as he considers it’s his right.

Hey everyone, hope I can find some answers and support here as this situation is really exhausting me both mentally and emotionally.

I am doing a short semester of studies abroad and managed to find a room in Berlin with a fixed term contract for not so expensive 520euros warm.

I signed a contract with the landlord and joined his flat (I’m basically renting a room at his place) in September and I’m leaving end of November.

However two issues appeared soon enough..

First one being that 20 days after I moved in he told me he would have to increase the rent by 40 euros for the next month as energy prices rose. Without any notice whatsoever. The rent is supposedly all included.

Second is that he wants to charge me 10 additional euros per night when my girlfriend stays here. Even though she would stay less than 5 nights per month.

I had a chat with a lawyer and read through several post, and it seems that as long as my girlfriend doesn’t stay more than 6 weeks on average at my place she is a guest and consequently my landlord can’t ask me to pay extra.

For the first point I don’t think he can increase the rent on a fixed term contract where it’s warm rent. Especially without notice.

I have included the contract (with all sensitive information blurred out)
at the link here:
https://postimg.cc/gallery/Kbvtrgj

He claims that having the fields (highlighted in yellow in the picture above) allows him to change rent as he wish and actually charge me for my girlfriend overnight stays.

But according to what I have read these clauses are illegal hence null. Am I right here ?

I don’t speak German fluently so it’s quite hard to find help and support in this matter.

I will greatly appreciate any reply or upvote!

Thanks for reading me.