You should use the wpForo Threaded Layout, not The Extended.

You can set forum layouts in top/parent Category settings. Child forums’ layout depends on the top category (blue panels) layout. They cannot have a different layout.

I'd suggest you read the documentation, you need to know some base things to be able  to create a professional community:

• Extended Layout
• Simplified Layout
• Question and Answer Layout
• Threaded Layout 

we are struggling with our new forum comments.

What we want is for comments to be shown as threaded. 

In our topics any reply posts show as separate posts without connection to the original comment that we are replying to. We attached an example. 

How would we make that possible?