Your site config
baseURL = '' # Set this to something like https://example.org/
relativeURLS = true # Why? Delete this line.
[[menu.main]]
name = "About"
identifier = "menu.about" # See my previous comment.
url = "about/" # Change this to pageRef = "/about.md"
Your templates are a bit of a mess. Read about base/blocks, or see this detailed example.