@kacemlight I know it's a very old topic. Just replying because i faced a similar issue. SEO tools pointed out that the heading structure was incorrect i.e the nav bar headings had H3 and content had H2 and H1.
I solved it by creating a barebones plugin and overwrote the tpl file that had the inconsistent heading structure (in my scenario). The path of the file is plugin/static/templates/partials/menu.tpl