How can I improve clay soil?

He has already applied topsoil. The clayey soil is further down.

Make sure you loosen the soil with deep-rooting plants like founding and soil organisms.
After the construction, water also stood here. In 2018, I had a lake on the play area after the rain. It resolved by itself.

I understood it as the topsoil already being very clayey and not brought in separately as topsoil.

Hello,
We have about 50 cm of topsoil (which is already clayey) and then about 1.5 m thick layer of clay.

I had overlooked that.

Under dense grass, the clayey soil does not become rock hard so quickly, especially since it is watered there. Open soil is mulched. Underneath, the clayey soil has always remained receptive for me.

We mixed in about 10 tons of sand with the milling machine on approximately 180 sqm.

We have had a lot of rain for 2 days now and currently we no longer have waterlogging.
Apparently, the sand has loosened the soil and made it more permeable to water.

The new problem is that the soil has risen quite a bit due to the 10 tons of sand.

The ground or lawn is now higher than the terrace and water can no longer drain properly there.

Does anyone know a trick on how I can remove about 3-5 cm of soil without removing the sand that is in the topsoil??

I don’t want to take away half of the sand again.

Yes, I should have removed the soil beforehand, but I neglected to do that.
Therefore, I now need a good tip to solve the problem.

Does anyone of you know a trick on how I can remove about 3-5cm of soil without removing the sand that is in the topsoil??

No. How is that supposed to work? You could try to recompact. It is still more permeable with sand in it than without. Of course not as good as it is right now.

we have already compacted the soil and rolled over it with the lawn roller.

Would it be an option to wait now until the sand has washed into the deeper layers and then, for example, use a core cutter to remove only the first 3-4 cm of the soil?

That way, we wouldn’t remove so much sand and would get directly deeper with the soil.

Would it be an option if we first wait until the sand has washed down into the deeper layers and then, for example, use a probe cutter to remove only the first 3-4 cm of the ground?

If the non-sandy part of the soil is clayey, silty, that takes years. Or is that a lot of gravel?