Time - Every xxx seconds of game time

What type of variable do i need to start a trigger every xxx seconds ?
Real variables do not work.... Am I able to use variables in events ?

The answer is: just start a repeating timer with xxx seconds (can be a variable). Now create a trigger with the event timer abc expires. and the action "run trigger x checking conditions".

Next question: can i manipulate the timer anyhow ? I can start and pause it. But i did not find any way to set the timer at anytime to x+2 seconds or something like that

I didnt quite catch you.

You can't declare variable's in events unless you add a event manually

Ok i managed it somehow... next question: how can i destroy a timer? i can pause and start the timer saved in a variable ... but how to destroy it ?

I think there is one called Countdown Timer - Destroy.