Question about graphic card slot on motherboard?!?

I saw your earlier post about cutting a piece off, that's quite drastic! Can the white part be moved at all? Slid in or out?

I tried sliding it but it won't help. There is another plastic in the end preventing it to be slided.......

That is a locking device meant to secure your GPU in the slot when inserted properly. Push the end to the down position. When you insert the GPU (straight down), the lock will move upward and lock onto the tab at the back of your GPU connector. Good luck!

ya you u have to lift it upward to insert the card jst like COLgeek said  
its same like you have for RAM slots

What you mean by "down position "? You mean push it towards the motherboard? But the thing is that the plastic is not moving a cm.... so I can't insert my gpu with the plastic is on the way. My gpu has this L shape and the plastic lock accepts
only rectanglar shape unless I move the lock out of the way somehow.

If that is the case, then the board is defective. That lock should move to function properly. You have 2 options. Return the board or remove the lock. The lock only holds the GPU in place and therefor can be removed without causing a GPU connection issue. However, it would likely void the warranty. Your call. Good luck!