After a couple hours search for a common solution to set brightness of my brand new notebook on Linux, I came to a simple and obvious solution.
As many tried, all common solutions for Linux will not work so, I found something that solved the problem.

Install and use Nvidia driver. After you installed, simply open the nvidia configuration utility which is in your WM’s menu and you’ll find the solution under X Server Color Correction. I reduced both brightness and contrast and got a good result.

Coo ha.. 🙂