Could someone tell me how to make for a example a cave to be dark? So it wont be lightened by the global lightning? Tried to understand that myself but it didn't work out.
You can create a dark area environment (don't make it global, you can set this in the properties). If you give it a higher priority (you can also set this in the properties) than your global one, it gets activated when Geralt enters it.
Area environment aproach is better, but then you have to be catious otherwise you will get same effect like in original game when you were entering and exiting caves. I would advise using a couple of additional area environments near entrances with higher priority to make transition smoother.