Refusal of building acceptance due to outstanding work?

when is the defect supposed to be fixed?

always withhold as much + x as you yourself would cost. At the end of the day, the cleaner won't come until Dec 2020

I’m afraid that too, that I will be chasing after some workers forever.
I want to move in within 3 weeks and not live with this situation in the living room forever.
Painters still have to come again, etc., you can see the touch-up paint, and so on.

So what I still haven't quite understood: were the windows moved because it was a (subsequent) wish of yours or because they were not installed according to plan and you then insisted on having them moved (according to plan).

In the first case, I can understand the general contractor not wanting a delay - however, I would then not understand why this has so far been at no additional cost to you.
In the second case, I would - quite clearly - stay firm and not accept it.

So what I still haven’t quite understood: were the windows moved because it was a (subsequent) request from you or because they were not installed according to plan and you then insisted that they be moved (according to the plan).

In the first case, I can understand the general contractor not wanting a delay – however, I wouldn’t understand why it has been without additional costs for you so far.
In the second case, I would – quite clearly – remain stubborn and not accept it.

There was no "plan" for the windows and it was more of an aesthetic defect (the inner window surface was much too deep, resulting in hardly any windowsill being present, the reason was the very deep roller shutter housing of the Raffstore). After a threat with a lawyer, everything then went very quickly and everything was moved without cost. Whether they moved it out of kindness or for other reasons, I don’t know. At least I was never told that I had to pay for it.

So it’s rather a mixture of both cases you described... Of course, I would first try to remain stubborn until they can legally/contractually object to me.

with lawyer

...Oh, with this kind of interaction, one should know the background(s)...

That all sounds too complicated to me. Why should I bother with that?

because you are only allowed to move in once the house is reported as completed to the building authority, and you can only do that once it has been accepted. and because depending on the situation, you may not be allowed to move in because you might not have the right of habitation. moreover, moving in is practically equivalent to an (defect-free) acceptance. if you build according to VOB, the subsequent trade must report defects. if the subsequent trade simply starts work, the preceding trade is considered accepted as defect-free. are you already painting? possibly the plastering work is already tacitly accepted as defect-free.

"with lawyer"

...Oh, with this kind of treatment, one should know the backstory(ies)...

Well, I said that I would involve a lawyer if they did nothing. Whether I really would have done it, I don't know. But the threat worked. I believe nothing works without such threats otherwise...