valid web address. I added a background image to my page. When I tried to add the same background to the header, all images, words disappear on the page and the head image does not appear.
Probably the reason for that is your custom CSS.
instead of inserting background images using custom CSS, please use the built-in options from the customizer.
Insert the image as a header background image through the Customizing ▸ Header ▸ Styling…Header Background Image menu https://prnt.sc/pqzyqe
also, insert the same image as a Body background image through the Customizing ▸ General ▸ Body… Background menu. https://prnt.sc/pqzzu0
after you inserted the image on these two places,
Insert the following code into Customizing->General ->Additional CSS: