I see your problem hopfel, It's the screen resolution indeed. I'm beginner in programming and I have some interrogations yet about this.
I have to add some kind of .ini to lets users changing resolution as they want. (or switch to windowed version)

Ha, I have a solution for you, press number 0 key and move the camera with arrows.

Thx to loopix for the terrain_multitex! I converted the script to be used in lite-c mode.