Well, I sovled the issue by myself.
If you are sharing a Bookmark, other user have to add it over the Repository Button. It is located three steps left beside the add Bookmark Button.
From there you can choose " Show shared items" and click on the Bookmark tab in the same window.
There you can see all available shared bookmarks and you just have to add it over the options menü right beside the Bookmark.
Hope I could help you with this.