how can i disengage from a combat if i am flanked? Rules state that to disengage i must ferform a shift directly AWAY from the enemy, but thats not possible if im engaged both in front and from the side. is that possible to disengage in such situation?

It is not. One of the built in benefits of surrounding your enemy. Personally, I've found that disengaging is fairly situational as unless you have a mobility advantage on the dial, they are just going to charge you again the next round.