If you can make a new folder, that's good. You haven't messed up, and it looks to be easily fixable. I suspect your graphics card might be causing problems with hardware acceleration for Ubuntu 3D.
Can you get to the login screen, or have you enabled automatic login?
If you can:
1. Click the Ubuntu logo at the side of the username.
2. Select Ubuntu 2d.
4. Report results back.
If you can't:
1. Press Ctrl-Alt-F1
2.Login at the text prompt (you can't see the password, just keep typing).
to restart the login screen. You'll need to enter your pass, again, you can't see it.
sudo service lightdm restart
4. Use instructions for if you could use the login screen, ('if you can', above).