That's really quite helpful!
But I still have a question left... not sure though if you can help me with it.
Doing heightmaps isn't the problem itself, but often it happens, that my ground isn't flat... I mean I make hills and all, but the ground has everywhere some sort of echelon form. Even at places, where it would be all flat, there are those stairs.. I'm not sure hiw to describe them, English isn't my mother language sorry ><
But I added a pic so you can see what I mean...