Bending-resistant base plate driven over by truck in less than 1 day

That went badly. A truck with concrete trusses has no business on the fresh foundation slab, I agree with you on that. What confused me was that the problem starts with your coordination of the earthworks. Your developer has a personnel and machine deployment plan, which you have "challenged" several times. I'm sure he won’t think so highly of you as a client anymore. Unfortunately, not a good start. I wish you that your house turns out well anyway.

Thanks first of all. The problem is that at the first inspection by the site manager a few months ago it was said: "Let’s finish the earthworks first." Only the site manager did not stick to that. The first time he came was about 5 weeks ago and, because someone else had dropped out, he tried to pressure us. But the earthworks hadn’t even started yet. Then he came again about 3 weeks ago and made pressure again because again someone had dropped out. Unfortunately, this time with success, because the earthworks contractor was already at work and said he could somehow manage if he was given space. Not even that happened, and the earthworks contractor quarreled with the site manager because he couldn’t continue. And he still can’t today. He pulled his machines out and has been working elsewhere for 2 weeks now. And it will still take several weeks before he can finally finish the earthworks. But that’s not even what I’m concerned about, the site manager is discredited to me, the company doesn’t respond to any emails. However, the workers (foundation slab teams, bricklayers & carpenters) have done clean work so far, except for a few small things. But you can talk to them kindly if you have questions and they don’t obstruct like the site manager. It’s unfortunately still about the foundation slab, which is really giving me a headache. And I don’t know what I should do about it. : I’m also less concerned about the ceiling, that’s why the whole paragraph was bracketed and doesn’t fit the topic.

You have had stomach pain for weeks and have done nothing. Either you finally get a professional, or you get antibiotics because you will soon get ulcers.

But by now the concrete is so hard that it probably doesn't matter, otherwise build yourself a hose level and measure the horizontal warping of the slab where the Wonder truck stood. If it is under 3-4cm, it might calm you down.

I am quoting myself again to clarify the original question:

[...]
Nevertheless, since we have not received any confirmation from the developer and the roof structure is already in place because everything is moving very quickly, we are considering having an expert report done for the foundation slab. Can anyone with experience say something about the costs for this? I would set a deadline for the developer to respond, and if he does not react by then, have the report done at his expense or withhold the costs from the final payment.

The only question is whether I am allowed to do that.

So you should have at least some idea. Whoever orders pays. If this expert finds a defect, you report it to the builder. If they acknowledge it, you're lucky; if not, then go to court, but a new expert report will be created, which usually takes 1-5 years. In the meantime, construction is stopped. Are you sure you're building with a builder? Because then you have no say until handover.

Please explain to the OP first the difference ... I don't think it is a property developer, but a general contractor or something like that, otherwise the OP certainly would not have been allowed to do earthworks on the property themselves ...

Why do you have the expert? They should be able to measure something there, that's what they are for, right?

What is a GU? We simply have the house "built by a company." But we took the earthworks out of the contract because we need services that the company does not offer. However, the earthworks contractor and the company already know each other and work together frequently. Only the site manager seems to be new.

Our building expert unfortunately did not tell us any concrete measures regarding the truck that we could have taken. She only included it in the report because she should have seen herself how the truck drives on the base slab. Our pictures did not help with that.