caused the computer freezed when press fn+arrow or fn+f3/insert. took a few reboot early to get back on.
That's a good sign, it seems that the code does something. But your DSDT is a mess, you've added the WMI device to the wrong place. Other code is missing.
Here is the DSDT from Slice, with the brightness code it is probably the same, try it. But, I recommend you to create a new DSDT with the brightness code.
DSDT.aml_SLICE_brightness.zip 21.24KB 2 downloads