Well just like the title says, i cant get into 1920x1080 mode (fullscreen) using the MGE tool. I dont know how to fix this. If anyone has a solution to the problem i would highly appriciate it.

What happens if you select the 1920 x 1080 option in the menu? Is the option just not there, or does it just not work?

It could just be that your computer/monitor does not support that resolution, but I'd assume that you must use 1920 x 1080 on other things if you're trying to use it on Morrowind.