I have a question, I have a forum that for some time when a user wants to publish a post, it takes a long time to send, it's like it keeps loading and new messages are never sent in new threads. I don't know if you could review this, since it is very slow when it comes to publishing topics
Since your site seems reasonably fast, i can guess that new topics and posts create email notifications and that is the reason.
A slow email (out) delivery.
You can debug that using some smtp plugin and check the logs provided.
Also you can install
and see other possible reasons for the slowdown.