What are maximum G forces humans can survive?
I read that very high g forces could kill a pilot, brain pushing into
  the skull.


High G-Forces cause blood flow to the brain to be impeded due to blood pooling low in the body under high acceleration. This causes the pilot to black out eventually. 


  Is there a way of decreasing or surviving these forces and how would
  it work if you ignore aircraft capabilities.


Yes, most if not all modern fighter pilots wear G-Suits. The basic principal of operation is to constrict blood flow to the lower body to prevent pooling in a high G maneuver to increase blood flow to the brain. The g-suit typically buys the pilot about 1G of increased tolerance. The average human tolerance is between 3G and 5G. Aside from possibly some aerobatic planes I dont know of any civilian or commercial aircraft equipped with G-Suits. Generally speaking good heart health can help mitigate the effects in sustained G situations. This why it is so vital that fighter pilots be in top physical shape as fighter planes are capable of very high G maneuvers.   

You can decrease the overall G-Force experienced by altering your maneuver (i.e. not undergoing as much acceleration). However in a combat situation some high G maneuvers may be warranted and thus the suits are used. In civilian flying all deliberate maneuvers are well within human limits.   


  If not what is the maximum survivable g force with current
  technology.


This depends on the exposure time to the G-Force, see this question/answer.