I didn't know my displays native resolution and thought to try them one by one. I chose the first one, and now the gui is a small rectangular at the center of the screen (all the other is black). I tried to reboot, but after "startx" I got to the same gui, without being asked again about resolution. Then I opened a terminal and tried "xsetup.sh", but there is not much space for the display and I can't see the cursor. I typed in blind "15" and pressed enter and it went to the next question (about mouse setup). But this time I try to type "1" (for usb mouse) and press enter, but nothing happens. In conclusion, I don't know how to correct the resolution setup.