Hello Klaus,
when you are in "Intro" Tab in your content type, then on the right hand side click number 3 "Typographie + Typography on Label"
Then next to the article image fulltext field there is a selectbox "None". Here choose "Image".
On the little "+" you can choose what to display: Image, Thumbnail1 ...
Try that to display the image and not the file path only.
Let me know if it doesn't work.
Cheers from Bavaria
gerhard