Interior plaster on the exterior wall is not complete

Is it a wastewater pipe, right? Can't it be turned off again? (Sorry if this is a stupid comment, no idea if that's possible we have all pipes in the wall.)

Otherwise, you'll really have to do the rework yourself. I would do it.

We have the problem in three corners: 1. Ventilation pipe wastewater 2. Exhaust pipe gas heating 3. Ventilation toilet + 2 flexible pipes of the solar thermal system According to the site manager, neither the drywall installer nor the foil is supposed to be wrapped around the pipe, and this foil should be glued to the plaster on the left and right of the pipe. My concerns: In the ceiling and floor area, the airtight layer is not complete....

People, people, people,.... What would they have done 20 years ago?

Just plaster the corner out a bit (doesn't have to look nice) and then box it in with drywall. Then it's airtight for your blower door test and done.

People, people, people,... What would they have done 20 years ago?

The same, see Wärmeschutzverordnung from 1995, §4...

The same, see the thermal insulation regulation of 1995, §4...

And even there the corner was just a bit knocked out.

Yes, that is really exaggerated, just throw it away and that's it.