It was a common issue that was reported by millions of users, it happens due to the overheating issue which means the heat absorbing components dried of sooner and than its usual five year life.. so because of the heat generat the ribbon pins are heated always it a high-voltage pixel burn.. Solution to this would be replacing the heat absorbing sheats and then replacing its AMOLED panel.
This is a common manufacturing issue on S20 series. So far the only solution is to replace the display. Sorry to say this, but If you are out of warranty, you may have to pay around Rs. 125,000 for an original display replacement at a Samsung service center. I'm suggesting to you use your current display as much as you can and make sure to backup your phone data to a somewhere secure place in case your display is completely lost. Meanwhile, try to use Link to Windows or Samsung Dex when it possible. Sometimes It'll be helpful to slow down the display usage and possibly help to use last long the display. But this is not 100% sure and can't guarantee. Just a suggestion.
