You can try to set the resolution manually by passing command line parameters, for example:
(Low resolution window) :
-screen-fullscreen 0 -screen-width 800 -screen-height 450
(Full HD fullscreen) :
-screen-fullscreen 1 -screen-width 1920 -screen-height 1080
Sorry for my late reply, I have been away for the holidays and got behind in replying.
You mean you don't know how to add command line parameters to the EXE? Here you have an explanation:
https://www.lifewire.com/command-line-parameters-video-games-3399930
(They are using a shortcut as example but it works the same with and EXE file. If you wish to create a chortcut, you can first right-click the EXE file and choose "Create shortcut", but it's not really necessary. It can be handy if you want to quickly be able to select several different resolution though).
