Construction costs for the shell structure - turnkey Kreis Wesel

Then they can make me an offer and ultimately I will decide.

Do that. But get independent advice in the process. So have the offer thoroughly checked. Finding the hidden pitfalls yourself (if any) is not easy – due to lack of experience.

Maybe a shell construction also makes sense and the rest is done by yourself.

That is also an option. If you are willing to accept the factor "time" as a financial buffer until one or the other room is "perfect," you have good opportunities with the shell construction to react to unforeseen events and do not have to have everything implemented "immediately" according to the contract.

Don't know if it's still of interest, but the thing with the shell construction and "accepting if one or another room... over years... is not perfect," think about that carefully. So think about whether you can really both live with it and want to.

One of the top 3 points of conflict in the new house is exactly that. People wanted to save money, do it themselves, and then it doesn't go fast enough for themselves or their partner... you have to be the type of person who can live on a construction site for years, even if it's only the outdoor area. We are still walking over gravel and euro pallets into the house nearly 2 years after moving in.

Don't know if it's still of interest, but the thing with the shell house and "accepting if one or another room... over years... isn't perfect," think carefully about that.
So think about whether you can and want to live with that.

One of the top 3 points of conflict in the new house is exactly that. People wanted to save money, do it themselves, and then either they or their partner get impatient... you have to be the type of person to be able to live on a construction site for years, even if it's just the outdoor facilities.
Almost 2 years after moving in, we still walk over gravel and Euro pallets into the house.

Thank you very much for your honest feedback.

Maybe a shell house also makes sense and the rest is done by ourselves. Ultimately, I will get advice from the respective providers. [/] Then they can make me an offer, and in the end, I will decide.

A shell or prefabricated house only makes sense for exactly two types of builders, namely the DIY king and people whose taste and/or budget have an almost zero overlap with the construction service description and sample selection of their general contractor. Only a few providers even have the "necessary" multi-level / multi-brand strategy like Seat-Skoda-VW-Audi to be able to make you such a tiered offer. Mercedes does have a Renault in the form of the Citan, but not a Talisman as well. Upgrading a move-in ready house from a shell can be more expensive than upgrading from a prefabricated house. The wishful thinking of some builders is modularly more scalable than reality. Every brand has a speed range tailored to its target group, and outside of that it is price-inefficient.

Almost 2 years after moving in, we still walk over gravel and Euro pallets into the house.

Then check if the divorce lawyer's business card is already stuck on the refrigerator side.

(...)
Then see if the business card from the divorce lawyer is already stuck on the fridge side.

No, why would it? I would estimate that in well over 40% of the houses in this development, the driveway/access road is not finished yet.
That's why I always have to shake my head when I read along here.

One is not finished with everything by the time of moving in or at the latest a year afterwards, especially not the outside. That is more the exception than the norm.