Hello everyone (sorry for bad english),
will try to explain my problem: I saved 3 PDF-files from a website and worked with them (added notes etc.) Also exported those notes to LibreOffice. Zotero created an PDF entry. Later I added an higher-level reference entry "website" and attached those PDFs (3 different entrys for 3 different PDFs). Now I get 2 References per PDF in the Libre Office bibliography. How can I fix that? (already clicked "Datei nach Metadaten des übergeordneten Eintrags umbenennen" for each PDF)

Website-entry (still incomplete, I know...)
https://s3.amazonaws.com/zotero.org/images/forums/u11081656/gwfmjiba056jwdk548un.png

Pdf-Entry
https://s3.amazonaws.com/zotero.org/images/forums/u11081656/j1hkkxt48c8bcpffbn8b.png

https://s3.amazonaws.com/zotero.org/images/forums/u11081656/batzubcjz1hdaouyp0k8.png

Bibliography:
https://s3.amazonaws.com/zotero.org/images/forums/u11081656/6v9agfndpjvbouz47blp.png

Thanks for helping a beginner :-)