- open the terminal(ctrl+alt+t)
- type the command "sudo gedit /etc/default/grub".
- a new dialog box will open.
- edit the line "GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"" to "GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor""
- save the file close the editor
- run the command "sudo update-grub"
- and you are set, just reboot.......
plz hit like if it helped
If you face any kind of problem plz comment and i would love to resolve your problem........