heyo, just bought the game and when I opened it put the wrong resolution in the settings by mistake. Now whenever I open the game the app goes in the top left of the screen, doesn't let me move it to where I want and "duplicates" the mouse, so that there's two cursors that are not in the same positions but move together. If I try to move the game cursor to "settings" to try and change the resolution, the cursor that is not on the game screen just minimizes the window. I tried deleting the config.dat file in "my games" but it didn't do anything. Any help?

In my opinion you made the right thing, because the config settings should be stored there.
Are you sure you deleted the correct file? I mean, if there are multiple users on your system, you may have multiple config files. Moreover, are you you sure you delete the file when the game is not running?

That said, what is your desktop resolution? Could you temporarily change it in order to match the game's resolution in order to display it correctly and edit its settings?

E benvenuto su GOG!

If Underrail is completely removed from your machine, that should reset any settings you've applied using the menu.
SOME games keep some files in your HDD after the uninstallation process. Make sure everything is gone.