When you choose the file and press “hochladen”/“upload”, it then returns to “1. choose Zeitschriftenrubrik”. This can be one of two problems:
1) The article can't be uploaded
2) The server is full, there is 6 GB space

What do I do?
You try to upload the next article on you list. If this one is WORKING, then the other article has problem 1. If this is also not working, probably it is problem 2.

1) Don't know jet. Try with another user.
2) Go to “Delete extra articles from server” and do what is says.