Floor plan planning shortly before submitting the building application

That may be so, but you still have to discuss things with the customer, advise them, show alternatives, etc. I can't just simply draw in furniture, then later see "oh, it doesn't fit at all," leave the furniture in place and just plan duct shafts right in the middle of a room. That is not acceptable.

There are good and bad architects, you have to decide which category you belong to yourself.

Is there this wall breakthrough? If yes, the pipe definitely belongs in there.

I will take some photos of the situation tonight and post them here.

I really feel sorry for you, sometimes you really think only amateurs are at work...
Have the pipe removed and placed inside the wall, as it should be.

That’s slowly but surely how I’m feeling too. First the nonsense with the tiny patio doors, now this. Let’s see what the new expert might still be able to save. He was recommended to me by Traumfaenger and has worked well with him.

one may ask why a ceiling opening of 35 x 15 is needed if afterwards one wants to go into the wall opening of 20 x wall.....

It is quite simple: because in the ceiling opening, within the ceiling thickness, the drain pipe from the bathtub (above the desk, i.e. on the upper floor to the left side of the plan of the wall) into the floor-to-ceiling wall recess of the ground floor is shifted. You have basically described it yourself: afterwards the ceiling opening one wants into the wall opening. During the passage through the ceiling, the drain pipe must have double the space next to itself, coming from the left and continuing to the right.

The clad drain pipe on the wall also threatens on the to the left side on the other side at the exterior wall,

Correct – with the subtle difference: we spoke about this, and for the obvious reason, it does not lie in the exterior wall. At this point, it lies correctly "in front of the wall" – perhaps someone then thought they didn’t need to look at the plan, it would be the same on the other side.

The site manager informed me that they would take a look at it and examine alternative solutions.

one will take a look at it and check for another solution.

Take a look, check?

He is supposed to saw a slot where one is drawn. And then swing the pipe in there, as it is drawn.

Look at it, check it?

He is supposed to saw a slot where one is drawn. And then swing the pipe in there as it is drawn.

He says that apparently something went wrong there and he will take a look at it. Then he will have the specialist company come again to make the necessary corrections.