Debian :: Can't Adjust Screen Brightness Using Fn Keys?

When I first install debian I couldn't change the screen brightness at all not manually nor with function keys, but I tried some of the solutions I found on the internet and now I can change the brightness manually (from the power management or the battery icon) but when I use the function keys it takes them like 2 to 3 minutes to respond and cause the system to hang (even mouse curser not responding) and then I'm forced to manually reboot the system, here is some information :

Code: Select all$ ls /sys/class/backlight/
acpi_video0  intel_backlight
 
Code: Select all$cat /etc/default/grub
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

[Code] .....

And I've tried this:

Code: Select allsudo -i kwrite /usr/share/X11/xorg.conf.d/20-intel.conf

And I add the following in this file

Code: Select allSection "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"
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