Average sound insulation? Walls, floor ceilings, doors

One can make some mistakes with component connections like ceiling / wall, screed / raw floor, etc., which weigh far more heavily than the difference between the laboratory values of sound transmission through material X or Y. What was the alternative for which the general contractor recommended the mentioned materials?

Mit dem GU sind wir die Fenster noch nicht durchgegangen.

Sure. He doesn't want you to back out because it all becomes too expensive for you. He will earn more on the shell construction than he gets in commission from the window dealer, so for him, the efficiency of the package of measures matters less than you "investing" where it benefits his margin :-)

Vollspantüren sind vollflächig gefüllt = mehr/durchgehend Masse = Schallschutz.

Nonsense. The tubular profile provides more stiffness than the additional mass that would have been inside without the tubes.

Nonsense. The tubular profile provides more stiffness than the extra mass that would have been inside without the tubes.

Not nonsense at all. Mass is what counts.
Look at any door program that specifies the sound insulation rating.

In terms of stiffness, the solid core door is also superior. That doesn’t mean that hollow core is bad. However, with hollow core, take a look at the door beforehand in raking light; with cheap models, the tubes often show through.