Should the land be filled up or not?

I received a call yesterday from an employee of the GU, asking me to please take a look at the new site plan; they wanted to inform me that due to the property, a change had occurred so that the house would now have a 5 m distance to the neighboring property instead of the previous 3.5 m. Because the terrain needs to be supported, this change is necessary.
I initially "accepted" it and asked what could be done now. The employee on the phone told me that unfortunately nothing could be changed about it.

Where does this change suddenly come from if nothing can be changed, i.e., who created this surprising need for action?
I would probably terminate a contract with a GU if they just shifted my house by one and a half meters after we had agreed on the position.
presented a less dramatic and, from my superficial point of view, feasible solution in post #19. This corresponds with the ground floor floor height recommended in post #2 by , which is why I consider doubts unnecessary until proven otherwise ;-)

h. who caused the unexpected need to act?

He only told me yesterday that the site manager had pointed it out. He had already been here once for the site analysis. He can’t explain why no one had noticed it until now.

I have already saved the drawing from #19. As I said, I will deal with it together with the general contractor.

The general contractor is very reliable; so far every single agreement, no matter how small, has been kept, even if it was only verbal.

I definitely want to give him the opportunity to deal with this together with us.

I don’t want a “who is to blame” discussion with the general contractor. I want a solution.

I don't want a "who is to blame" discussion with the general contractor. I want a solution.

Very commendable.

He just told me yesterday that the construction manager had pointed it out. [...] He cannot explain why nobody has noticed it until now. [...] I definitely want to give him the opportunity to deal with it together with us. I don't want a "who is to blame" discussion with the general contractor. I want a solution.

It is still not clear to me WHAT exactly needs to be dealt with. I dare say that where besides me also saw no problem, there wasn’t one. So: have there been any crustal shifts on your property in the meantime – where does a sudden height drama come from? – to my understanding, someone must have created a problem (my God Walter, Bodo with the excavator again?) if there was none before. Only who and what exactly, that is still completely unclear to me. I’m at a loss as to WHAT the construction manager has dreamed up.

It is still not clear to me WHAT exactly is supposed to be the problem. I dare say that where, besides me, even saw no problem, there was none. So: Have there been any crustal distortions on your property in the meantime – where does this sudden height drama come from? – According to my understanding, someone would have had to (my God Walter, Bodo with the excavator again?) have created a problem if there wasn’t one before. Only who and what exactly, that is still completely unclear to me. I am at a loss as to WHAT the site manager dreamed up.

I don’t know myself, I didn’t understand what was supposed to have suddenly changed there! I was so surprised by this info that I only later understood what he was actually telling me!

But I will clarify this directly together with the general contractor next week.

I just walked past the property and saw that the L-bricks (circled area), which secure the area to the houses in the back row, are broken through in the middle and are now slightly leaning forward; the paving there is also obviously affected.

The private path belongs as separate property to the respective owners of the houses in the second row.

Who is responsible for these L-bricks? The owners of the houses?

I am concerned that we will be blamed for it once it actually starts..