can't login to terminal password issue

First off I'm new to Linux (only been using it for a couple of days) so I don't really know what I'm doing. I'm trying to install Nvidia drivers.

The file is set as excecutable but needs to be run by root.

So I used sudo -i and logged in, but when I type my password it says password incorrect, but if I hit enter again it works and I'm root.

Then I ran the file (sudo sh name.run) but it says I have an X server running.

I looked it up and it sounds like I have to access the main terminal (ctrl alt f1) to end it.

When I do this it asks for my account, which I put in. (Nathan)

Then it asks for my password and I type the same one that worked logging in and in the other terminal and it says incorrect.

 I've done this several times so I know I typed it right.