But what I miss is building up a closed and stable front.
I guess I often saw enemy units slipping through the areas where armies or detachments of my side were in position. Is it possible that in trench warfare enemy units can move through my frontline?

After I recognized these behavior I choose the intercept rule in the options. Now I saw the little arrow in the oder-section of the army but I cannot activate this oder. The tooltip tells my that this is not selectable in trench warfare.
What am I doing wrong and how can I stalemate enemy armies?
By the way I had 16 event cards after patching to 1.05a. Is this ok?
By the way 2: In 1.04g I could use stosstruppen. After patching I guess it wasn't possible anymore.