Pile up on the property before the notary appointment

Thanks. It’s not soil, that was the term I chose as a layperson. According to earthworks, the ground is suitable. hm.

Sure. He tells you what you want to hear. If he dumps the soil at your place, he doesn’t have to haul it away expensively and possibly pay a lot for disposal.
You will still have excavation for your house too?

In the end, having 40, 50m³ delivered can be much cheaper than disposing of 10, 20m³, especially if he dumped contaminated soil on you...

PS:
I had 10m³ of topsoil delivered six months ago for 200 EUR, of which 80 EUR alone were for the truck + container rental.

It should be gravel.
Regarding the question: do.
The municipality doesn't care at all what is currently happening with the property. And ultimately nothing is happening. You are not causing any damage either.
Do!

What is one supposed to do with gravel on the entire property if in the end the garden is supposed to be there as well?