[Kibbols123]

Is there a way to close a specific forum, but allow users to still post in the topics of that forum?

[Stephen Edgar]

Maybe this plugin will do what you want 🙂

bbPress Protected Forums adds a metabox, shown while editing a forum, that allows you to disable new topic creation for determined user roles. The plugin is perfect for those situations that you may want your users to see the list of topics of a forum but don’t want them to create new topics.

https://wordpress.org/plugins/bbpress-protected-forums/