Hello,
by now I can provide feedback on the matter. After the ground was inspected by a road builder with experience, he himself, like , said that the topsoil is not suitable as topsoil and we should simply cover it up. Since we will have a lot of slopes anyway, our flat area will be limited, so the costs for obtaining topsoil will be manageable.
Basically, we plan to compact during the filling process.
Due to our development plan and after consultation with our construction company, a slope as I sketched in the initial thread is not possible. Unfortunately, we will have to make the slope less steep and plan 1-2 berms with at least 50 cm.
Unfortunately, only slopes alternating 1 to 2 and 1 to 3 are allowed here. After consultation with a site manager in road construction, it should be sufficient without greening, without the slope sliding. However, to prevent ruts from forming due to rainfall, he still recommends greening. For the "gentle" slope, even grass would be suitable. We have not yet concretely considered how we will implement this later.
A friend of mine, who has a similar slope, is thinking about planting ivy because it supposedly has strong root growth and grows quickly but only quite shallow.