I tested it on other Theme and it worked. But later I actuated it after running the system status and made the updates it required and it was brocken again. I think the problem ist coming fron the ‘product-thumbnails.php’ file.
I found the problem ! The ‘flowplayer.min.js’ (flowplayer5/fronted/assets/flowplayer/…)
ist not compatible with any version (from ‘1.9.1’ to ‘ of ‘jquery.min.js!. But I need ‘jquery.min.js’ on my website, so I can’t do without it !