How does dynamic rendering work? Here is how it works according to Google:
Dynamic rendering requires your web server to detect crawlers (for example, by checking the user agent). Requests from crawlers are routed to a renderer, requests from users are served normally. Where needed, the dynamic renderer serves a version of the content that’s suitable to the crawler, for example, it may serve a static HTML version. You can choose to enable the dynamic renderer for all pages or on a per-page basis.
How do you implement dynamic rendering? You can read the step-by-step instructions in this section of the help documentation.