Whoever looked at it gave me the advice to leave it just as it is. I thought about it but couldn’t help it. I felt that it needed to be removed.
It was in two cement layers. After removing the first one humidity was getting visible and the smell was not the nicest also.
Under the second one I found soil. But the surface is a mix of soil and lime. Underneath I found finally the native earth used to build the house. It’s colour is dark brown and contains only a little quantity of clay. But the clay seems pretty strong.