My game graphic quality has dropped significantly since the last timee I played. Do you guys know why that has happened and how can i fix it? (I'm not using any mods)
Chances are the screen resolution was lowered within the windows/linux OS itself.
For windows just right click anywhere on your desktop if you have windows7 or higher and go to display settings and you can see if the Display resolution is set to "recommended"
In Linux it may depend on Which distro you're running. But if you're asking for help about resolution chances are you're running a windows machine. As most Linux users would already know where to check for their respective distribution they're using.
But typically it should look something like this
Desktop menu > Preferences >
Screen resolution.
Also make sure you're not launching the 32bit version of the game.