Raising / leveling the building ground - is that allowed?

In the case of a slight slope, is it allowed to raise or level the property? Can this be done with the soil excavated for the basement? Are such measures (600sqm property, only slight slope, if it can be called a slope) costly? Is this allowed?

This would result in a difference in height compared to the neighboring property. Or, if this is not allowed, could the property be raised by 2-3 meters up to the property boundary, secured there, and then the last meter be made level again to the border of the neighboring property?

The neighboring property would, by the way, currently be an undeveloped meadow (formerly agricultural land). It could become building land in the long term, but certainly not in the next 5 years. Regarding the possible road layout, this meadow will, if at all, only be developed as building land many, many years from now.

If it is relevant: Saxony.

Depends on your development plan. Cannot be answered in general. It is forbidden in our development area. However, we do not have a slope,...

And what if it is not regulated in the development plan?

Oh, one more thing: The house would actually hardly or not at all change in height. The house is already located "at the beginning" of the property on the high side. It's more about being able to level the garden then. Is something like that partially also prohibited? And for the garden, "softer" soil would also be suitable, right?

If no specifications are made in the development plan, you must specify your terrain modeling in the building application and have it approved.

If you want to change the natural terrain, you must specify the heights exactly in the open space plan of your building application. It should not be a problem as you describe. The costs are also not that high, depending on how you want to secure your fill, always open upwards