[pmcreations]

I would like to create more than one ‘forum’. How do I do that?
or Do I have to do that in groups? – I would rather not. I would like to have the option of each forum in the menu.

[@mercime]

Then install bbPress the plugin (sitewide forums) https://codex.buddypress.org/getting-started/installing-group-and-sitewide-forums/ and have group forums as well.

== I would like to have the option of each forum in the menu. ==
Do you mean the main menu? Then use custom menu and add the link/s to respective forums.