Can’t open the post when clicking on catagory

Hello to you, dear Reader and hopefully problem-resolver!

I write a post, categorize it and it will be shown at the start.

But when I go to another site I can’t go back to the initial page. Clicking on the link under ‘categories’ it only shows up some text, but not the complete post. Clicking on the headline comes out the “error” page.

What did I wrong?

https://www.theconversationcircle.com

Another point is, that under each post comes out “no comment”

How can I change it?

Thanks a million and regards