Site Feedback / Navigation Ideas - Squarespace 7.1

Site URL: https://www.health-qi.com/

On reaching the homepage there is drop-down list for navigating the website but only under the word 'Therapies'.  Clicking on any of the other choices; Mindset, Body Chemistry or Physical, will take you to a page with a number of buttons enabling you to choose where to visit next.

The reason for this current navigation set-up is because there will only be 20 - 30 therapies, so that list and its associated drop down will be fairly small, whereas there could be up to 100 sub-pages under each Mindset, Body Chemistry or Physical heading, and this wouldn't look good as a drop down.

I have considered using a mega menu, and I'm as yet undecided on that option.  I could also use Squarespace's search function, however, having spoken with their technical team the search function does not always work correctly and index all pages, so that method for locating the page you want to view can't be relied upon.
 

I was wondering how other people would approach this navigation problem, and what solutions there might be.  Any general feedback on the website would also be appreciated.