Please type first during the game "armleuchter" and afterwards
you have the following Cheat combinations: 

Code             Effect
----------------------- 
Ctrl+Shift+H   - to more weapons factor special is increased.
Ctrl+Shift+U   - More vehicles are available.
Ctrl+Shift+A   - Factor special increased.
Ctrl+Shift+W   - to the next mission.
Ctrl+Shift+X+Y - more cash is available.
Ctrl+SHIFT+S   - firing strength and armoring for all ehicles increased.
Ctrl+SHIFT+F   - all trees burn.
Ctrl+SHIFT+G   - gas attack.