How can I increase user participation in my forum?

Hello people, please, I have a forum that has good content but a very low participation of users in the form of publications and responses to publications. Even when I set up a system to reward the posters, I get a very low response from them. It is also difficult to get new members to register, since they only use the resources of the site and leave. How can I make them participate more in the site? Valuable suggestions will be appreciated. This is a link to my site for reference https://classhall.com/discussions