Baunebenkosten calculation realistic?

Do you have more detailed information about the installation of WP and underfloor heating?
Laying distance and flow temperature?

No, not yet.
What do I need to pay attention to?

And which air-water heat pump is it? It's best to read something about [Luft-Wasser-Wärmepumpe] here. And the settings. You can save some on additional costs there. Controlled residential ventilation is omitted? A tip. Room height. Costs hardly anything but gives an incredibly good room feeling.

https://www.hausbau-forum.de/threads/vergleich-erdwaerme-mit-lww-pumpe.36071/post-429645

You don't need a controlled residential ventilation system, you only need an exhaust motor, for example in the bathroom, and forced ventilation through the windows and doors inside the house. That's enough. Experience, not hearsay. If I were to build again, I wouldn't install underfloor heating in the bedroom, but a radiator with a Danfoss thermostat; underfloor heating is far too sluggish, either it's too warm in the bedroom or it's too cold. Now we regulate the bedroom through the open window. Also not exactly ideal.

Then you should do the thermal balancing.
That will fit then as well.

I would not take underfloor heating in the bedroom, but a radiator with a Danfoss thermostat, the FHZ is far too slow,

And then? Are separate circuits with the heat pump reasonably feasible? Because even with maybe 28 degrees supply temperature, you can't "just quickly" heat/cool the bedroom with a radiator.