S23 second hand display issues

Hi all, my younger brother bought an S23 from a website called BackMarket for £250, but I've realized that the screen was replaced, as the bottom bezel is bigger compared to our dad's S23. I also noticed that when I put the brightness all the way to 0, the icons on the blurred background are popping out too much, looking really washed out. It looks almost like the icons are squashed instead of blurred, and sometimes I see some graininess.

Also, the 120hz doesn't feel like 120hz. It is a little bit choppy when I scroll up and down in the settings and feels less than 120hz I dont want to say that it feels like 60hz but probably less than 90hz. ​Do you think this is all because of the poor quality display, or is something wrong with the phone? I have some pictures, but I can't attach them as the icon is grayed out.