Hi Victoria,
thank you for your help.

I tried the first link but nothing obviously changed on the page.

The part at the second link workes. As you can see, I have know preview pictures of the posts.

After using the next snipped i get this failure;

Deine PHP-Code-Änderungen wurden aufgrund eines Fehlers in Zeile 21 der Datei wp-content/themes/enfold-child/functions.php zurückgesetzt. Bitte beheben und versuchen, erneut zu speichern.
Cannot redeclare avia_change_category_blog_layout() (previously declared in wp-content/themes/enfold-child/functions.php:13)

I am a littles step further thanks to you. How can I progress know? The position and the size of the pictures are not optimal. And a textpreview would be super.

I am looking forward to read from you.

thanks.

Ronny