Seal the slot in the screed

Hello everyone, next item in the Sanierung/Umbau project. To lay new pipes, we made a slot about 15cm wide in the screed. In the pictures, you can see the slot where no new pipes have been laid yet. How can this slot be closed again? There must be a few things to pay special attention to, right? I definitely trust myself to just fill it, but I would like to know which material etc. you would recommend. Thanks

Screed would be a good idea

Two bags of screed from the hardware store on top and done

Hm ok. You read so much on the internet, hence my inquiry.

Hm ok. You read so much on the internet, so my question.

I know exactly what you mean. Impact sound insulation can no longer be properly achieved. And all that stuff with screed clips and treating the edges with resin, I don't know if that's sensible. What kind of flooring is going on top?

Parquet goes on top.
But I should fill the bottom layer again with Styrofoam between and above the pipes, right?