Hello, DBO 1.0 version is a very old game using a very old 2004 engine (Renderware), he does not have a proper 4k + Widescreen, or multiscreen support.
If you have a Widescreen or use more than one screen, that's mainly the issue.
The only hotfix that we have available, is playing the game on Windowed Mode with Vulkan + Windows Scaling set to off.
Unfurnutelly, if you have More than one screen or uses Widescreen, the Fullscreen mode will not work as intended.
We say sorry for the issue you have, it's not your fault, but it's not our server fault either, unfunutelly, is how the game was originally programmed to work.
Vulkan activated + Windowed, will fix some issues you have and make the game playable, but won't fix all of them