Now that the OP has calmed down a little I do think I can help.

First, I have had this happen with a failing mouse AND with a failing graphics card. I had 2 monitors on my system and lost the graphics card, leaving all my parameters and libraries off on a 2nd monitor I could no longer use (the emergency card only supported one monitor). The only thing that brought them back to the single monitor was setting the system to Launch to Factory Settings.

The 2nd circumstance was with a failing mouse. I dragged the preview screen above the menu in error and had a heck of a time getting it positioned correctly again.

First, using the arrow on the right of the preview screen, set it to Floating.

Now, you should have it floating somewhere on your screen, and you can drag it where it should be (in all that blank space below where it is now). Keep a tight grip on the mouse, hold the left mouse button down and drag the preview screen. When it gets to a place where you can safely drop it, that section of the screen will become highlighted. (On my screen it changes to a blueish grey color). You can release the mouse button when you see the highlight and your preview screen should be where you need it.

Once you get that accomplished, we can see what needs to be done with the parameters menu and library.