Recalbox not working properly on "DVI" screen

[proplayer2020]

I tried to make a portable console with a Dvi lcd screen.
Recalbox works, but i have a big gap between the right end of the screen and recalbox menu/games. I tried using a theme but its the same problem.
Here are images :
https://ibb.co/cwF5NX2
https://ibb.co/wRJ99tC

You can see a black gap that takes 20-30 % of the screen.
I tried to change recalbox user config and i looked to tutorials but none worked for me.
Any help would be appreciated.

[proplayer2020]

i forgot to mention the screen is conected with HDMI and
has an external power supply.
I also put a theme "480p" because the screen is 800x480.

[proplayer2020]

Found the problem, follow this tutorial :
https://wiki.recalbox.com/en/tutorials/video/tft/hdmi-tft-screen