The contractor wants to issue an invoice for planning services

What exactly was agreed upon at the end?

In the initial post, you write about an offer from the contractor.

Was this accepted despite faulty description and planning?

If not, no contract was concluded and therefore no payment obligation.

The expenses of the GU are offer costs, since there was no agreement with the AG about the contract content yet.

There are documents. They were handed over. The T&Cs must also be included there. There is no response to that here :(

It doesn't matter. Just because an offer was handed over, no contract has been concluded.

Hello everyone, I haven't been able to keep up with answering you.
We did not accept the offer that was made to us.
There is nothing about this in the documents, what happens if the contract does not materialize or something similar. I just checked again especially. Is that what you meant with your question? There are also no terms and conditions. Whether the construction description has been legally reviewed from his point of view, I doubt. It is a really small general contractor (3-man operation), and whether any customer has ever signed the incomplete standard construction description in this form, I also doubt (or he was very naive).

If no order has been placed and no prices have been mentioned and not even any indication of possible costs has been given, I wouldn’t pay either. You must at least be informed.

If I have a kitchen planned at Ikea, it costs money. But that is clearly communicated. If I get an offer from a kitchen studio and they don’t tell me beforehand that they want money for even a simple offer, then I wouldn’t pay afterwards nor would I pay for an offer for a house if nothing was communicated.

Some craftsmen nowadays also want money for cost estimates. But that must be communicated to the customer beforehand so they can decide whether to pay or not. Friends also had the idea to build a house and they had to pay for more detailed planning at two house construction companies, that is, before signing the purchase agreement. But that was clearly communicated as well.

There are also no terms and conditions.

O..keey... Well then. I'm curious. Let me know how it turns out. If it's just a small 3-person company, then they probably won't have a legal department either ;)

It is like this: The minimum requirements for a contract include two matching declarations of intent regarding (at least) performance, consideration, and the price, the so-called essentialia negotii. Of course, contracts can also be concluded orally, implicitly, or by smoke signals. However, the contractor bears the burden of proof for this. In this case, you have very good cards.