@o4n, This is just my way…
Google is always looking for the text hierarchy of a website and to do this it looks for h1, h2, h3, h4, h5, h6, p. Most sites don’t use all of these but most certainly h1, h2, h3, h4, and p.
What I do is redo all the styles to h1(main heading), h2 (sub-heading), h3 (sub-title), h4 (captions), and p (paragraph text) and assign then the font style, font size, font-weight, font, alignment, etc… and the HTML tag of h1, h2, h3, h4, and p. Now that I have done all that I can get on with assigning these styles to my page content.
Looking at your site I would remove the header out of your navigation area and place it on your page and assign it main heading (h1) which google looks for to know what the page is about. I would then assign a sub-heading below it to give me more information about the page and assign it h2, All the remaining headings on the page would be sub-title (h3) and all the small reading text p.
I could go on and on with this but the above is a good start and maybe also read this - https://www.iteracy.com/blog/post/anatomy-of-a-web-page