Does the builder have to hand over the soil report?

So grass is already growing? If not, wait, the grass will do that.

Grass is already growing and there are still puddles!

Spotwise? Make a small soakaway 1 meter deep and fill it with loose sand.

Large-scale? Work the soil extensively with a sponge and sand.

And get earthworms

What kind of subsoil do you have?

I assume that the OP wants to see the geotechnical report exactly because of this question. The seller does not have to let you see it as a buyer. I also assume that he does not have one. No one is obliged to obtain a report. A (good) general contractor / building contractor requests it from their client, a good client has it created because this secures the warranty on the structural engineering. However, I also think a report is not necessarily needed. You just drill down deep and go to the garden specialist store you trust. Whoever wants a lawn garden will have to do a lawn inspection every year. Next year it will be the lichens, then the mushrooms, and before you know it, it dies during vacation and is dominated by weeds.

Thank you for the many messages

Yes, I want to find out with the expert reports what kind of subsoil it is.
We assume that it is a very clay-rich soil mixed with stones and is very hard and firm

I always thought that the soil survey had to be done.

The problem with waterlogging is on about 1/4 of the lawn area; the rest is not really a problem.

So we should work with sand in the areas where there are problems to loosen it up
Before spreading the sand, then use the spoon to perforate the soil so that the sand can penetrate better, right?

What should we use?
Those shoes with the spoon underneath or should we use something like the lawn woodpecker where you always pull out a kind of sausage of earth?

Don't you have any pictures of the earthworks or has any of the neighbors dug a hole? The problem with compaction is that it can be deep, and that partly determines how you can solve the problem or not. If the subsoil is compacted, you can do as much as you want with any 10cm spoons and sand. That won't get through the 30-40cm of topsoil. With that, I would see the symptom rather than the cause, because it should be loosened by tilling once. At least in the area you can reach with superficial measures.

If the water does not infiltrate at location A, it helps you little that a drilling was done 20m away at location B for an assessment.

Short answer to the question of whether the developer must provide the soil report.

Yes, he is legally obliged to do so.

Why? In the case of a developer contract ([Makler- und Bauträgerverordnung]), it is a consumer construction contract according to the Building Code ([Baugesetzbuch]). And there, a soil report is among the documents that must be handed over.