Brightness control (Fn + left_arrow/right_arrow) Acer aspire

I have Ubuntu MATE 16.04.1 on my acer aspire es1-531 laptop. I noticed that despite all the other Fn+ keys are working, the screen brightness does not.

does it work when you run in terminal

xbacklight -10


xbacklight +10

but i asking about the keyboard, i can change the brightness in power manager but the keyboard(fn+left/right) is not working.

i tried to modify the grub acording to this
but no results for me.

I mean if it works, it means you dont have a driver problem.
And you can add custom shortcuts in the settings menu to change your brighness