Maybe it is because the background can not do PNG or my resolution is not right because before the link was JPG all I did was use an image format converter for high quality.
Note I have tried images/Background.png lowercase instead of the upper case it did not work.
Yeah sorry just saw that you already mentioned it.
CSS background-image can be jpg, png, svg or whatever else format, so if the image is not showing, you might have the wrong image path. Can you post a screenshot of your folder structure showing where the .css file and the image are located?
On a side note, it’s impossible to improve the quality of a jpg by converting it to png, the png will have the exact same image information as the jpg.