Pioneer News Theme doesn't show my pictures

Hey there!

I recently installed the Pioneer News Theme for my blog. (https://wpsam.com/freewordpressthemes/pioneer-news/)

Blogadress: https://www.theartoffreediving.com

There is a slider integrated in the theme, which should show the pictures in my articles. But neither in the slider nor in the Home Page, pictures can be seen. The article introductions are just containing picture placeholders. When I click to a certain post and get to it directly, I can see the pictures normally.

What can be the issue here?

Best regards
Sebastian