Thanks,
meanwhile i have still found the solution, but thanks for the reply.
For those who want the right answer, VertexNormals is one solution
But there is another, more practical solution. Just go through the tutorial: layered materials.
It is short, easy to understand and more common and it explains exactly how to cover materials with other materials depending on the gradient of the surface.
Link: Unreal Wiki: Layered Materials
Kind regards