Secondary primary top horizontal menu that only shows up on specific pages

I would like to know if and how it is possible to make a secondary primary horizontal menu? that only shows up on specific pages. The goal is to create kind of a secondary wordPress site within a WordPress site, the reason for this is that I saw a video on YouTube, https://www.youtube.com/watch?v=B_yOha8P-dI. In the video it is explained that you can SEO optimize your website if you create a special link structure on your site that corresponds with Google My Business. The “secondary WordPress side” Will have content with keywords that gets a lot of searches and has low competition. Is this a good approach?