Construction Costs for Single-Family House - Is Our Cost Plan Realistic?

Are the prices realistic for the size?

Are these individual quotes you obtained yourself from craftsmen or is it an offer from a general contractor/general planner showing the individual items like this? Did you round for the forum or are the numbers that exact? All gross? More information about the scope of services is missing for evaluation, not only but of course also for electrical work, see #6.

Are these individual offers that you have requested yourself from craftsmen or is it an offer from a general contractor/general entrepreneur who lists the individual positions like this? .... 6.

A general contractor/general entrepreneur does not list individual items.

A general contractor/general turnkey contractor does not list individual items

Ours does, if only so that you can decide what you want to do yourself or what you save by doing so.
Of course, they have an electrical package and do not specify every meter of cable. It only states in the construction services description, for example, how many sockets in total, how many light switches, etc.
Otherwise, for example, it says laminate material 20 €/m², which you get reimbursed if you don't take it, the same for tiles, etc.
In our case, the individual labor costs were also listed separately, for example, tiling work for bathrooms and area x for a total amount Y.
This gave us the option to opt out of the tiles, procure our own, and have them installed at the stated price (just as an example).
This way you were still very individual and could save on materials or labor.

Tiles, sanitary and electrical are clear. But for example, it does not include screed or a roof. One belongs to the building, the other is the equipment...

Ok, the one was shell construction with roof = 1 price, which was unbeatable anyway. As for the screed, I can't tell you off the top of my head, but plaster, doors and windows were definitely separate, as were heating and water.

I have obtained quotes from companies for the individual items. Amounts are rounded, gross. I am mainly concerned with the shell construction price, as I had expected it to be lower.
By the way, electrical work is without KNX.