so I didn't know about scaling stuff with screen size until I'm further into the development. So that's my bad that fullscreen gets you problems, I designed it for 720p.
To solve your problem you have to delete your entire save, should be in AppData/Local/Packages/[girls frontline shootout]/LocalState under "playerPrefs".
You can go ahead and delete that which will delete all your saves. Sorry for the trouble!
[Side note, you can use "tooktheredpill" code in the settings to unlock all game content :) ]