Hello, thank you in advance to anyone who helps me with my questions.

1. Does anyone know why the second navigation bar is permanently displayed even though there are no subcategories?

2. I am also interested in how I can create my own fillable category fields for certain forums.

3. I would also like to know how I can integrate statistics below a forum.

1 hour ago, TobiasEU said:

1. Does anyone know why the second navigation bar is permanently displayed even though there are no subcategories?

You have some sub-menus on some entries. That’s why it’s there. If the submenu would only appear with some items, it would constantly appear and reappear and push the site content up and down while you hover over the menu. You wouldn’t want that. 

#2 Custom fields per forum is not a default feature.  

There is a Marketplace mod for it.  You can browse Invisioneer.org's Marketplace Directory to see if you can find it.  

#3. If your account has the proper permissions, you can use the Block Manager.  You should see a small arrow on left hand side of screen, which contains menu of several default widgets and blocks you can add anywhere to the page.  One of those is the forum statistics.  

Thanks for your help @opentype & @Joel R.