Land planning / floor plan planning

I just have to see what I can use to evaluate them.

I can't give you a search term here yet in which posts I have explained that. But if you look for my posts in the section "Erfahrungen mit Baufirma XYZ", you will find something.

Just because they don't have a nice homepage doesn't mean they have to be good at the same time.

Yes, it's not a guarantee. But you will quickly notice that the "I'm a mason, not a web designer" and the "I don't care at all, not even about the homepage" websites differ from each other.

Is it common to ask for references there and to directly ask former clients about their experiences?

Sort of. Of course, they don’t have communication departments for reference management, and the GDPR has caused uncertainty in many small companies. You see references with open eyes when you walk through the new development areas in the region of the construction company.

Ask around among acquaintances, in new housing developments, at the sports club, at the hairdresser, at the dentist. Anyone you know who has built in recent years. Important are those who have similar expectations. You can be satisfied and your buddy says, what kind of idiot did you recommend to me.

It is important that you know what you want and decide accordingly. Homepage and references are just building blocks on the way to the right building partner.
You can have a technically perfect house, with a smooth process and still not be satisfied.

Good - thank you very much.

I will now also give some basic thought to the layout again. All beginnings are difficult - and/or I am too unimaginative ;) But things you do for the first time are usually not done perfectly.

It is not the floor plan you need to worry about.
Do you want to open a catalog, point at it and move in, or actively decide and be on the construction site? Both are possible with a general contractor, but from a certain point on you need an architect.
Do you want a specific energy standard, a wall construction, a building material?
Are you the type for whom the water from the hardware store faucet is the same as from the designer Überalles faucet regardless of cost?
Every general contractor has a scope of work and a standard. The more the standard and its philosophy fit you, the better the value for money, and the better your satisfaction with your house.
Standard – wherever it is – is less error-prone for the craftsmen than exotic options.

You need a room program. How many meters of closet, how big is the bed, what is the minimum spacing, etc.

also consider whether you want a show kitchen, ala I prepared something in the second kitchen, or an ergonomic functional kitchen that is the social center in the open space. In the first case, all women stand in the second kitchen to help and talk.

Do you want a specific energy standard, a wall structure, a building material.

I would like to have KFW40+ – simply because I think that probably won’t be wrong in the long run. Wall structure and building material are "whatever" to me, probably because I don’t understand the differences. So I need to inform myself much more. Can you recommend good literature for a prospective builder? I am willing to engage intensively with the subject – but it doesn’t have to be a degree.

Are you the type for whom the water from the hardware store faucet is the same as from the designer Überalles faucet regardless of money?

I am the type: I want something high-quality, without it necessarily having to be designed by a well-known designer. Otherwise, all under the motto "who buys cheap buys twice" – it should be high-quality, without overdoing it.

Every general contractor has a construction performance description, has a standard. The more the standard and its philosophy suit you, the better the price-performance ratio is, the better it is your house with which you are satisfied.

Understood

You need a room program. How many linear meters of closets, how big is the bed, what minimum distance, etc.

Ok, I will make a plan with my partner… The bed is still the simplest (waterbed 2.40 x 2.20). Closet meters – if it were up to her, 500 :) Since anything can still happen between 0 and 2 children here, we will have to remain a bit flexible there… and this decision regarding children should be deliberately left open.