ᐅ Floating screed / patching small areas

Hello everyone,

this is about a house built in 1973.

I mistakenly chiseled out a tunnel in the kitchen ceiling, right in the middle, to run water and wastewater pipes from one corner to the other.

I have now resolved it differently and closed the tunnel again, adding edge strips all around, polystyrene, PE foil, and then a quick-setting screed to decouple this “tunnel.”
As far as I can see, the original was a fully floating screed without edge insulation. Well, it’s been like that for 50 years.

Now I have two small holes in the floating screed that I need to fill. One of them is in the new screed I just poured because the soft-soldered copper hot water pipe was or had been leaking there.

The other spot is the floor opening in the basement for water and wastewater pipes to the new kitchen.

Can anyone tell me how to properly fix these two small areas (about 30x30cm (12x12 inches) or so)? Photos attached.

I was planning to lightly seal the floor opening from below with expanding foam as a “cover,” then fill the hole with screed. Is this correct so far? Or can you advise me on the easiest way to close it? Ideally nothing too complicated or time-consuming.

Thanks!