thanks so far.
The "??" was, because I copied it from the internet ...
But I noticed another thing. Of course I also looked at epubs created with calibre. And in this case, the content is all in the main path. But like suggested on the internet, I created an OEBPS folder to contain all the content. After editing the path in the container.xml file, the "version error" is gone (but therefore I found many other errors in the other files.
Thanks for your help.