If I may suggest something, with all those forums and subforums, and no content in them, it looks empty. It’s better to start small and add as content is being posted. Just my two cents. 😉
You should definitely fill those subforums up. I also think the theme looks broken, I'm not sure if it's just the style but it hurts my eyes and it's a bit difficult to navigate too.
Navigation looks fine to me and I appreciate a clean, simple style. But just to reiterate what others have said; you have almost 40 subforums and 13 posts. Reduce them down significantly or start posting in all of them. An empty looking forum will remain an empty forum as potential members will be put off.