Can my contract be extended without my (signed) approval?

Hey everyone,

I am in a weird position at work and would really like to get some advice from you. (longer text, I am very sorry)

I started a job last June that I mostly like. My contract was limited to a year, it states in my contract that "on May 31, 2022 the employment contract finishes automatically without previous cancellation being required".

So two weeks ago I had a lunch with my Senior Manager and she asked me if I would like to stay and how I feel about working there. I told her what I dislike about my current position and that I would either like to get a different grading or a salary increase or if that is not possible I would like to reduce my hours.

After our talk I had a week of holiday and now this week she handed me a letter from HR that confirms that my employment contract will be extended for another 12 months. I was baffled because it did not take into account any of the things we talked about PLUS normally (as far as understand) you will need to sign an extension. I just got a letter as a notification but it seems they do not need or want my signature to confirm the extension. Is that correct? Because obviously just with an extension my contract conditions (like salary or hours) would not change and I am not okay with that. Can I reject that extension and quit by June 1? Or is such a one-sided extension lawful even though I did not sign it? Is it necessary that I hand in my notice or can I just reject the extension?

A little bit of background:

- my colleague told me that normally that the "lunch" with my Senior Manager was already quite late because you will actually need to do it 2 months before you would leave.

- My Senior Manager told me she "sees what she can do" and when handing me the letter she just said "HR has already extended it"

- Normally your Senior Manager has to argue why you have to get a pay rise. A basic requirement for that argument is an end of year evaluation the Senior Manager does with the Manager (me). My Senior Manager has not done that with me (even though I asked for it) and therefore it is harder to argue for a pay rise I guess.

- It is stated in my contract that the notice of terminating the employment contract is normally 2 month.

Sorry for the long text. Do you have any advise for me how I can handle the situation? I would be really interested in what the law says about it and if you also think this situation is weird. I will obviously talk with my Senior Manager about that next week but she will probably give me a "there is nothing I can do about that" answer and I just want to know if I can leave by June if necessary.