Ok I still can't solve my unstructured supermesh. 
Therefore I created a simple example. 
I have these 3 layers.
Layer1 is the bottom elevation
layer2 is the  top elevation 
layer3 is the fault layer which divides the area in 2 parts 
layer1
"x","y","z"
1,1,0
1,2,0
1,3,0
2,1,0
2,2,0
2,3,0
3,1,0
3,2,0
3,3,0
layer2
"x","y","z"
1,1,5
1,2,5
1,3,5
2,1,5
2,2,5
2,3,5
3,1,5
3,2,5
3,3,5
layer3
"x","y","z"
1,1,0
1,2,0
1,3,0
2,1,0
2,2,0
2,3,0
3,1,5
3,2,5
3,3,5
2,1,5
2,2,5
2,3,5
In Feflow i create a supermesh and load the data into the maps panel. Then I open 3D Layer Configuration and I import the layers. 
It works but the fault line is not a vertical line. How do I have to prepare my data that I get a vertical line? 
feflow always interpolates and that is not what Í want. 
I hope my example is clear. 
Thank you for your help
Joscha