SEO headings H1-H6, how to set it up correctly?

Question

Search Engine Optimization

Hello !
Need help with micro-markup on the page
If everything is clear with h1 markup, this is the main heading (product name), and can be used once, but what about h2 - these are subsections of the page (we can use at least 10 times, if there is a large volume), now the most interesting h3 -h6- there is little information on this subject, many advise using them only if there are more than 10,000 characters (in my case, about 7300), is it correct to use them as subheadings in an article or is it better to exclude their use (stop only at h1, h2 )?
Here is a link to the screen - https://drive.google.com/file/d/1dA1SRVP-_oFnK_Evw...
Perhaps h4 is superfluous, but h3 are subheadings. Is there a restriction on their use? What happens if the setting is wrong?

Answer 1

No, there are no restrictions on how to use these titles - Open the book you like and see how the Content is implemented, each nested line is the title of a section, chapter, volume, and so on. The main thing is that the h1- h6
tags are the highlighted part of the text that displays the main idea on the page
.

Answer 2

These are just headings of different levels, they are strongly used as you need