Cloudflare can only cache certain files, but it cannot speed up sites which are generally slow. While not really twenty minutes, your site still takes more than ten seconds to load and that is something you have to fix on the server side.
What you could do is employ some HTML caching, as that would also cache HTML, however that heavily depends on your site and whether content is dynamically generated or not. Typically one should not cache HTML. You seem to be using Wordpress, so you could also have a look at Welcome · Cloudflare Automatic Platform Optimization docs , that won’t make the site faster but would automate caching.