Final invoice for shell construction (200 sqm, clinker, without basement, roof) ok?

Don't understand the question.

You knew the price before it started, didn't you?
( Angebot ?)

Or do you mean he will give another 20% discount if, in your opinion, the agreed price is not right?

Don't understand the question.

You knew the price before it started, right?
(Offer?)

Or do you mean he will give another 20% discount if, in your opinion, the agreed price isn't right?

mhh, I roughly know how much material is needed, but I don't know if 3000+ skilled worker hours are necessary and so on. I lack the comparison...

Yes, and we still don’t know exactly what was built and what the final result is.

And, you didn’t just place the order, but also had an offer available ... right?

3000 hrs = approx. 15 weeks with an average of 5 people (40 hours per week), if construction took place in summer, then maybe only 12 to 13 weeks, because the people were there longer than 8 hours daily.

The skilled worker hours should also be included in the offer

I find 40 euros cheap
Roughly estimate how many people were on the construction site daily
The time is not unreasonable

How am I supposed to describe the final result? House, faced brick, roof on, 200 sqm screed inside, plastered? Of course there was an offer, but compared to the final invoice for the above services, it was exceeded by 10%. How should I therefore assess this?

I do not understand the answer to my question, yet it is interesting to me and an answer from which I will draw quite a bit myself.

By defined shell construction is meant:

Are earthworks included?
Is the shell construction closed?
Is the framework erected?
Why is plaster already applied? Is the electrical wiring already installed? Is underfloor heating included?

So which works are now summarized under your umbrella term?