If running Windows, can you still see the clock at the far right-hand corner of the screen ?
Modern laptop screens cannot be resized to lose one side of a display, the picture will automatically appear centralised and the screen will always force a full screen picture if possible, but cause text to appear twisted/stretched in some way.
If your clock and other desktop items have vanished off the right of the screen inside the black area, then it's your screen at fault and will usually need replacing, or the flat cable at the rear of the actual screen may need refitting/replacing, a simple job for a technician.
Some laptops have an ability to use software in the graphics card software to adjust the picture and move the display around, cut bits out, rotate it around etc. It may be worth checking there too.