Sorry if this is another newbie issue, but the layout seems destroyed on a particular page: the Vendor Membership page. It seems to be working fine on Android cellphone using Chrome. But not on desktop using Firefox. This page was working fine on the Pizza theme demo before this.
Also, there are spacing problems in the Vendor Registration page.
Also, the problem is also present in my admin pages. The header menu is covering some of the buttons below the header, thus preventing me from clicking those buttons. These problems were not present in the Pizza demo theme.