screen is not complete. I can't see my whole screen.

Is this a specific app that has part of its window outside the viewable area, or does it happen with all apps and windows?

If its a specific app, you can click on the top of the window and drag it out to see the rest of it.

If it happens with all apps, windows and even the desktop icons, then you may have enabled zoom.

You can hold down the command key and drag 2 fingers down on the track pad to zoom out.

If neither options works, then you may want to provide a screen shot so we see what you see.