Hello,

The header shown is misaligned because you contain a large number of menu items inside your menu row. That’s why the items go to the next line.

So, to fix this you need to use less quantity of items inside your menu. From Appearance >> Menus you can edit your menu or use sub items of the menu.

Your issue has been resolved. Go to Layouts > edit single product layout > edit product gallery widget and configure the thumbnail position.

Best Regards.