I have problem: i change screen resolution to bigger then my monitor support and i got black screen. So the question is: where i can change screen resolution and frequency (i mean config files)?

Just look for a file "config.cfg" in the Nexuiz\data folder. Open it with WordPad or whatever and scroll quite to the last lines. There you may find two files like that:

vid_height "1050"
vid_width "1680"

If you don't find them, just add them. And of corse you have to set the adequate values.

Or just remove them and it will use the default of 800 x 600 on next start..