If you have changed your file before having backed up and are experience problems, you can copy the /etc/X11/from the Ubuntu Live CD to your hard disk /etc/X11/file (before this, backup the file as described before).It is important to know what the capabilities of your hardware is before you start.
The open source community has decided to create their own open source video driver for Nvidia video cords, called Nouveau.
That way the commands will be in your terminal history.
You can then simply press up arrow on your keyboard to recover the key combinations.
I gave up and switched to the open source Nouveau driver. I really would like to remove nouveau but it wants to remove xserver-xorg-video-all It's unbelievable how unusable some computers become to beginners thanks to this.
This tutorial solved the problem but my sequence was different: 1. And there will be the constant fear of updates breaking Nvidia or possibly somehow reactivating Nouveau.
While care is taken by your fellow user to ensure that everything will work, it is more often than not likely the case.