(Lump sum) fixed price and VOB/Construction Code

did not consider circumstances (e.g. construction pit, access roads, soil conditions, slopes, etc.).

These costs are anyway borne by the client. The contractor covers a flat rate of 30cm (at least this is common)

In my opinion, that is money thrown away. All terms can be found on Google in a short time.

I have a different opinion: the crux is known to be in what is not stated. This also applies to the construction performance description. If you already have a construction supervising expert, usually the contract and the construction performance description are reviewed as well. You can also see this now with the terms lump sum fixed price and fixed price: what if there is a free pass behind it for the contractor?

You can see it now also in the terms lump-sum fixed price and fixed price: what if behind it there is a carte blanche for the construction insurance?

That is exactly my problem. I get these terms (once fixed price, once lump-sum fixed price) thrown at me by various construction companies. One also said that it is important to have a lump-sum fixed price. I find hardly any information about this on the internet, if there is even a difference. As a layperson, I can unfortunately make little sense of it. Of course, you can trust the construction company in this respect and it will probably work out. But I would like to somehow know exactly what I am going to sign.