Hello,

It seems that you have selected a header which allows the item to show behind it. So to fix this you can simply use some other header for product pages from Theme Settings >> Product Page >> Single product header.

And for the custom pages like about us you can directly change the header from the header options while editing the page.

To edit your mobile header you need to go to WoodMart >> Header Builder >>Your default header >>Switch to mobile layout.

Screenshot for clarification: https://jmp.sh/XEje3Kn

Best Regards.