Assessment of soil - Does the earthworker mean natural topsoil?

In my opinion, the civil engineering contractor is very competent. I only showed the photos to an independent third party. He said, "this is clay, it has to go"... this is not native soil, etc. He scared me a bit... now I'm wondering if he should have dug even deeper... do you think I'm making myself unnecessarily anxious? And in the end, he still wants to give me a "pressure test" to certify the load-bearing capacity of the soil. Is that the guarantee that it is load-bearing soil?

He will not build on clay, but will replace the clay with sand to a depth of about 80 cm. He compacts it with a vibrating plate and then places concrete on top.

No. Sand was placed directly on this soil. The clay was not removed. If it is clay...

Only the topsoil was removed...

I have not understood the problem yet. You regard your civil engineer as very competent. He gives you the good news that the soil is load-bearing. Then a third party unsettles you with a comment on a photo?

That is exactly it. Yes, I am unsure because of the assessment of the photo. Can't you tell from the photos whether the soil is reasonably load-bearing?

How is one supposed to see that from the photos? Just post your [Bodengutachten] with the foundation recommendation!