Hi
sorry to hear about your issues Pavo. I had the same with my kids, so I know how stressful it is -- it used to really wreck my days.
Info on your background could help as regards advice, but here is my story.
We are from the UK but really really loved living in Germany for 15 years. When our kids reached school age, it was really not what we imagined.
Our children not really embracing German, and not really being able to express what they were capable at home. We tried to interact with schools but it was always so difficult. Unfortunately I've never had any positive interaction with any German teachers - some people say its the system but my feeling is that teachers in Germany themselves are the problem. The money is there but the Teachers have 'wenig Bock!' (in the uk it's the opposite)
This was brought to a head by covid - 'many teachers in my kids schools refused to teach online as well'.
During lockdown my kids attended a UK online school and they really did well so...That set the ball rolling. 'Day and Night'
In the end we moved back to the UK, and my two are really happy and doing well in school. One is in independent and one is state
the education philosophy/method is similar and IMO is more positive and forward thinking than in Germany. Although general standard of living is a bit lower (but ...not as bad as the news would make-out)
Probably this is not an option for you, but my message is that interacting with teacher/schools in Germany is pretty pointless so if it comes to a head you have be prepared to find alternatives. There are often private or different school options that could fit.
Matt