Why when new themes are added does not show, you need to press CTRL+F5 what was updated, what is the problem?
URL?
ok, it appears you have enabled the "turn WP to wpForo". So you do not need fastest cache or any caching.
Disable that plugin and try again (after clearing your browser cache). Also keep in mind that Firefox can be an issue with caching in general.
your browser has been affected by your cache plugin. So the problem reason is either, the browser cache or the server side cache. In both cases, you should do a deep clean of cache or check it with different browser.
BTW, instead of deactivating the cache plugin you just need to exclude the forum page from your cache plugin, here is the instruction: https://wpforo.com/community/faq/wpforo-and-cache-plugins/