Work contract individual or lump sum?

The contract is only binding for you once you sign it. If, during the review, issues arise that you do not agree with, you simply do not sign. There have already been several cases here where the fixed prices were structured in such a way that it is practically impossible to meet the conditions. Or as the client, you are forced to accept things that will be expensive and that you absolutely should factor in beforehand.

Is a contract for work with a prefabricated house company individually tailored to a customer or does every customer at a prefabricated house company get the same contract? Can the contract be viewed in advance?

So you don’t have to have the contract checked separately (if it is fixed anyway).

Even though I cannot understand your resistance to the advice that you are not doing yourself a favor with the academic question snippets: the contract for work has two parts, one of which is the provider’s general terms and conditions and description of construction services. For these two parts the rule is: take it or leave it, there are no special concessions. The second part consists of the house design (which is very largely individual) and the selection of fixtures and fittings (which concerns the personal design within the specified description of construction services, and here there is also limited room for special concessions). Not having the contract checked in advance would be highly negligent; everything essential has already been said here on that. You are practically the prototype customer for the relevant consultants. I myself am more technically focused and construction method neutral; explicitly for prefabricated houses you are best served by Mr. Beuler, Mr. Freymuth, Mr. Zink or Ms. Wächterbach (the latter, however, is brand-specific, for Meisterstück) at the best addresses. Brand-specific for Hanse Haus Mr. Burmeister is a top consultant; the first three mentioned are, as far as I know, brand-neutral, especially Mr. Beuler (and the architect cooperative he works with) whom I have recommended here several times. If you were not so stingy with information about your project and also more communicative regarding your preference, you could (but I have already said this several times) be helped much more precisely. Otherwise, that is it from my side; everyone is helped only as well as they want.

Even though I cannot understand your resistance to the advice that those academic question snippets do not do you any favors: the contract for work has two parts, one of which is the provider’s terms and conditions and construction performance description. For these two applies: take it or leave it, there are no special treatments. The second part is the house design (which is very largely individual) and the selection of samples (which concerns the personal design within the specified construction performance description, and here is also limited room for special treatments). Not having the contract checked in advance would be highly negligent, everything essential has already been said here.

At what point in the construction phase are these contracts each signed? By the way, thanks for the really (!) helpful tips, even though you seem annoyed, which I do not understand. I ask the questions that are relevant to me. No one has to answer.

So you don’t have to have the contract for work and services checked separately (if it is fixed anyway).

Yes you do! It will be notarized, that means in the interest of the company, so that it is not contestable. But that doesn’t necessarily have to be in your interest.
Besides, an examination reveals what additional costs there are. Of course, you also have the option to negotiate something out or renegotiate. Once it is signed, it’s too late.

At what point in the construction phase are these contracts each signed?

Beforehand. Before the signatures, there is no contract and no certainty whether everything is as it seems.

By the way, thanks for the really (!) helpful tips, even though you seem annoyed, which I do not understand. I ask the questions that are relevant to me. Nobody has to answer.

As I said, from my side this was also the last answer to you if your behavior remains the same. There are people around here who would like to help — both the questioners and the readers. When the questioners break their project down into tiny questions (and distribute the relevant background information over their threads, so that it becomes a scavenger hunt and a memory game to keep track of), then this pleasure turns bitter. Simply because that is very exhausting (for me "just" annoying, for others — mostly neurotypical people, as is common in the population — frustrating). The fact that many are "too polite" to tell you this openly does not mean that only a few are bothered. And I repeat for the last time for you that you yourself would be the greatest beneficiary if you changed your behavior. Take a look at the threads of more skillful questioners to see how much more productive and purposeful help they receive and will receive.

At what point in the construction phase are these contracts signed?

At no point during the construction phase, which only comes afterward. The construction contract itself is only signed once, right at the beginning. The sampling protocol is signed much later of course, but by then the construction contract is already well underway.

At what point in the construction phase are these contracts each signed?

Why these contracts? If you mean the contract for the house construction, then of course when the house is completely planned. Basically final, and then there is only one contract. Like when you buy a car. The car/house is configured, then signed. At that point, no construction phase in the true sense has started yet, because that only begins much later. Compare it to the car being scheduled after the order and then being built at some point. Only with a house, the intervals are just a bit more stretched out. The final house is checked by the general contractor and so on... then there's eventually the appointment for the selection of materials... it goes step by step like this until the actual start, the construction phase by my definition.