Failed to start save/load screen backlight brightness of backlight:acpi_video0

when i start pc give mi this error

Please have a look at:

https://wiki.archlinux.org/index.php/Backlight#Kernel_command-line_options

and for how to add kernel boot parameters:

https://wiki.archlinux.org/index.php/Kernel_parameters#GRUB

For a similar issue, see:

https://bbs.archlinux.org/viewtopic.php?id=211967

Hope this helps!

I don’t know what your hardware is but on mine i just added acpi_backlight=video as @pebcak has shown with the info above.