Hi gediminas,

Thanks for posting.

Hold down Fn key and tap F10. Tap it several times to get different light levels.  If that's not working, try adjusting it through the mobility settings. Press the windowskey-X, and then selected Mobility Center. Slide the keyboard backlighting control to the right to turn it on - there are two settings, dim and bright.

Fn + F10 does not work :/. And linux ubuntu dosn't respont to windows key + X also. I've tried everything I could find on the internet so far, nothing works..

Unfortunately your initial post did not indicate you were using a non-windows operating system.  You should post your issue in the Linux/Ubuntu Forum for more expert answers.