For all of you guys out there using a small video display like this, it tested some different resolutions.
I found something really nice!
Open your nano editor in the Terminal and edit the :
as sample: sudo nano /boot/config.txt
Then we have to activate (You can activate something if you delete the # in front of a function).
Change the Resoultion for clear types:
For Games like open arena or super tux it would be better to change the resolution to:
STRG-X will closing the nano editor and asking if you like to save the changes or not.
You can save two of these config files and don`t forget the reboot after changing 😉
After reboot the display should be without black bars around.