Resolution change (Far Cry 5)

Can't change resolution below 1225 x 800.
Went into the XML file, changed the values. Run the game. Nothing has changed.
Once entered in the XML file. The values returned.
Then I changed the values and set the checkbox READ ONLY.
Launched the game ... and STILL have the RESOLUTION 1225 x 800 !!!!
Opened the XML file, all the values are those that I put down.
What's the problem, I do not understand.