Screen shadow or “ghosting” usually happens due to either a display setting issue, outdated graphics drivers, or a hardware problem like a failing monitor panel or loose cable; I’ve seen it happen after enabling things like motion smoothing or incorrect refresh rates, too. First, try updating your GPU drivers, setting the correct resolution and refresh rate, and turning off any weird display enhancements in settings. Also, check or replace your HDMI/Display cable and try another port. If the shadow is still there even on BIOS or another device, then it’s likely the monitor itself is going bad, and replacing it is the only real fix.