well i follow the intructions and i bind myself few commands and it seem it doesn't work, here is a copy from the begining to the end of my commands, so that you can see if im doing something wrong, note i change the file to read-only so that the file doesnt change when i run the game.
[Engine.PlayerInput]
MoveForwardSpeed=1200.000000
MoveStrafeSpeed=1200.000000
LookRightScale=12000.000000
LookUpScale=-12000.000000
MouseSensitivity=27.999998
DoubleClickTime=0.250000
bEnableMouseSmoothing=true
Bindings=(Name="D",Command="GBA_StrafeRight",Control=False,Shift=False,Alt=False)
Bindings=(Name="F2",Command="god",Control=False,Shift=False,Alt=False)
Bindings=(Name="F3",Command="slomo 0.4",Control=False,Shift=False,Alt=False)
Bindings=(Name="F4",Command="slomo 1.0",Control=False,Shift=False,Alt=False)
Bindings=(Name="F5",Command="jesus",Control=False,Shift=False,Alt=False)