Construction contracts - how reliable are they?

Good day,
my wife and I want to build soon. We already have the plot of land. What we are missing is a construction company. We are looking for a general contractor (GU), whether solid construction or prefabricated houses is not so important to us. We have already conducted some negotiations, but unfortunately, these always fail because of the contracts. Now we still have 2 companies in the final selection. One company from Cologne, which is not a GU but a construction cost optimizer (Argus Direktbau) and ID Massivhaus from Hamminkeln. We liked ID's pricing, but unfortunately, there are no reviews available. An acquaintance said that we should keep our hands off both contracts because one cannot speak of a fixed price guarantee here, which would be important to us.
Now my questions:
How can you find out if a company is reputable when there is no information about it on the internet?
Is there a way to check a company's creditworthiness or whether it has ever been insolvent and is now operating under a different name?
Should every contract be reviewed by a construction lawyer? In our case, we would quickly lose a lot of money, and you don’t always know immediately if a lawyer is good.
ID Massivhaus, for example, has no construction and performance specification, only a two-page contract. So far, we have only experienced that there were lengthy performance specifications for every contract. Without a construction performance specification, you cannot say what will be installed, can you see that differently?
The contract is also according to the Building Code, but how is it if ID, for example, does not deliver? Can you cancel any contract and then not have to pay anything after a certain time, or does this have to be explicitly stipulated in the contract? What if no contractual penalties are mentioned—who is liable if the construction is delayed?
And the last question: if you commission a construction cost optimizer, who is similar to an architect, and order each trade separately, who is liable if something goes wrong? Normally, a GU has to give a 30-year warranty on the construction and you only have one contact person. But how is it the other way around? Is the warranty given by each trade? But then, why does the construction cost optimizer provide a fixed price guarantee and a lengthy construction performance specification? Is something like this even reputable or realistic, precisely because every trade is commissioned separately?
Thank you for the answers.

Serious yes! Meaningful? Depends!

It seems to me you are confusing seriousness with your security requirements. There is no "comprehensive coverage" in construction. Consider your construction service providers fundamentally as partners and not as opponents. Otherwise, your construction will definitely be stressful for everyone involved, and stress reduces quality.

Regarding your questions and points:

Determining seriousness:
Of course, there are serious companies that need little more than a handshake to work well, and at the same time there are unscrupulous providers who describe services in full detail and "guarantee" them. References on the internet are certainly a good indicator. Missing references say nothing about the provider except that they do not engage in marketing in this direction. You will not be able to make objective comparisons – intuition about people helps. A sign of seriousness in craftsmanship is the enthusiasm and self-expectation of the actors for what they do.

Contract:
Contract comes from "agreeing". It must state what has been discussed and what will be performed. We have either no contracts or standard craftsmen contracts with our craftsmen. Consumer protection is quite strong in Germany. Your need for security seems greater – or is it bad experiences or mistrust? Usually, you don’t need a lawyer. If it helps you sleep peacefully: go for it.

Description of construction services:
The larger the provider, the more comprehensive the standard descriptions usually are. They are meant to give security to both parties. The description can also be included in the offer, which belongs to the contract. A description of construction services is not mandatory (and is not an indication of any kind of seriousness).

Liability for delays:
This can be stipulated in the contract – you will never be able to exclude weather. You will only get a fixed move-in date if a lot of "leeway" is allowed in the planning. Basically: obligations on the part of the developer are services that you also pay for.

Cost optimizer:
The cost optimizer is not similar to the architect. I would keep my distance from it. Putting the price too much in the foreground usually affects quality. Description of construction services or not. You are buying a house, not a price.

Warranty services:
Either a general contractor takes over the warranties and guarantees or the respective craftsman company in the case of individual awarding. How much these securities are really worth you only see in case of damage. With our first (terraced) house, the developer went bankrupt a few years after completion of the estate. A successor company took over the guarantees – the state of NRW was involved with the developer and thus assumed responsibility. In the current construction, we rely on established and respected local craftsman companies.

Phew, have you ever had direct, personal contact with construction companies? 4.6 face-to-face conversations?

We have already conducted some negotiations, but unfortunately they always fail because of the contracts.

Why? Is it because you distrust them?

but a construction cost optimizer (Argus Direktbau)

Construction cost optimizer... okeyyyy.... once again someone who jumped on a moving train and wants to be rewarded for something that is unnecessary...

How do you find out if a company is reputable when there is nothing about it on the internet?

By asking questions. See how long they have been building houses. Which neighbors have already had experience with them?

Should every contract be reviewed by a construction lawyer? In our case we would quickly lose a lot of money and you don't always immediately know if a lawyer is good.

You have to trust somewhere at some point. Where does your distrust come from?
That's not good at all. First therapy, then house building

ID Massivhaus, for example, has no construction and performance description, only a two-page contract.

Almost every construction company that builds more than 30 houses a year has a construction performance description. Otherwise, talk!

And the last question: if you hire a construction cost optimizer, who is similar to an architect,

I would not hire a construction cost optimizer!

the bigger the provider, the more comprehensive the standard descriptions usually are.

I cannot confirm that!

Don't make the mistake of only looking for a cheap optimizer.
Building a house can mean from and to, still you should not choose the construction PARTNER just based on the costs.

Hello everyone,

We feel similar to Tommyxx regarding the contract with ID. In the end, you can only trust, we think. Have you by now found builders who have already built with ID? We look forward to hearing how you decide and whether you were able to resolve your concerns or not :-/

Unfortunately not, we are still searching. How far along are you with ID?