Hi,
for those interested I have uploaded a slightly modified version of the collection theme.

I have done the following changes:

• Added a "back to top" link to the footer

• Category view (the article list) now shows the "feature image"

• At the bottom of the article there is a link to the next/previous article

*Added related items to the single article view

Note:
As i have also adjusted some text to my needs (especially for the german translation) the download also includes the language file.

You can see it in action and download it here:
https://en.ralf-kerkhoff-bilderwelten.de/news/collections-theme/

Note:
Site is not completely multilingual at the moment (it is a hell of a job to translate all the content)

Cheers
Ralf

Maybe something to join forces with the original author? Did you contact him?