Styrofoam granulate at different raw building floor heights

What kind of mat would that be? So if the screed thickness is e.g. 7cm, does it lie halfway up in the screed?
Good point about the anhydrite, thanks.

Unfortunately, I’m also at a loss here. Our screed layer laid them at critical points. It was a plastic cross fabric, exactly as it’s called, no idea. He placed it on top of the underfloor heating pipe.

A really silly question. I can’t really tell from the pictures how it continues next door.
Couldn’t you just remove this raised area completely so that you have both on the lower level?
Looks like there are hollow bricks or something similar on the floor in the picture...

As described, that is the basement ceiling. I wouldn’t chisel anything off there.

We also hoped that we could remove the raised area, but that is already the basement ceiling. The bricks are only at the edge, behind them there are no perforated bricks.

Oki.....otherwise you have direct access to the wine cellar, why not?? :D :D Then I would probably create the same level in a simple and inexpensive way. The question is whether you want to do it yourself, then I would do what I am also skilled at. Basically, you could put anything in there, even gravel or something else o_Oo_O, since it's only about reaching the actual floor level. From there, the real floor construction begins with insulation and so on. Or you make a beam layer and fill it in between with an inexpensive filler and put OSB or Fermacell or similar on top. I would reconsider filling the entire 28 cm with high-quality/expensive insulation; it would depend on the amount/cost. Beyond a certain thickness, insulation doesn't really provide much additional benefit. The owner of my former construction company once told me, regarding a similar question of mine about insulating/filling the spaces between the beams, to simply use sand. I then used expensive cork granulate and that was fine, but somehow I think sand would have worked just as well but for significantly less money.

A rather crazy idea: Could one simply fill the non-basement rooms with concrete up to the level of the basement rooms? And then have insulation of the same thickness everywhere. The idea behind this is that concrete (hopefully) settles less than insulation or screed.

Regarding the question about doing it yourself: I really enjoyed doing all the removal myself, that was truly a pleasure, but I prefer to leave the reinstallation to the professionals. I just ask and am happy about all the answers here because I want to understand it myself, to be able to join the conversation when the screed company suggests this or that. There is even a wine cellar, but it is located separately in the garden.

I think you could do that, however, you then have a lot of moisture in the floor and the drying process can take a very long time, which is why I would keep my distance from such a wet solution.
I believe the solution with the beam layer with filling in between would appeal to me, for example, foil at the very bottom, then laying out about 2-4 cm of Styrofoam boards over the entire surface and then placing beams floating on top at the necessary height. Between them, an inexpensive filling material especially for impact sound, and then continuous OSB screwed onto the beams. If the top layer (Fermacell/OSB or similar) is then uniformly at the same level for the other rooms as well, there should be no cracks at the edges. I think sometimes OSB is also laid/screwed twice in opposite directions.
Something along those lines would appeal to me, but of course, you should still gather various information about this; however, at the moment, I can see nothing that would contradict it.
The tradesman you consult each time usually tells you what he knows and what he would do with his usual materials; he rarely has to worry about costs because he can usually pass them directly on.
Take a look at various options for dry construction of a floor on the internet; there are countless.
Concrete would be absolutely out for the reasons stated above, and with 28 cm height, quite a quantity/weight accumulates.
A friend of mine built a larger podium for himself by laying Ytong stones flat next to each other on the floor and then tiling on top. There’s so much out there...... :D. You just have to "somehow" bridge this height and there are countless variants, from which I would take the simplest one for myself. Because of the risks mentioned here (cracking), I would design the top layer with OSB/Fermacell or similar. Whether a mat prevents this, I don’t know.