Dynamic content indexing

Question

Google

There is a site, part of the content on the page is static, and the other part is no less important, it changes randomly, as search engines treat it, because every time the page is filled with different content and keywords may fall out.

Answer 1

They treat badly.
Search engines want to provide links so that the user finds what he is looking for. And if the page is different every time - what will you find here?

Answer 2

If you change content a lot, even if some of the static remains the same. Generate the same url to this content, even if through #. Search engines are now smart, they know how to index this.