To return a borrowed eBook with Bluefire Reader, first bring up the lists list view in the above right corner of your screen. There will be several further options here.
Click onto the play-icon next to the eBook which you would like to return. Click onto "Return" ("Zurück") to give back the eBook. The eBook will be deleted from your device and your Onleihe account, and can be borrowed by other users.
In the Bluefire Reader click onto the information icon next to the eBook which you wish to return. Then click on "return item" (Datei zurückgeben").
Click again on "Return" ("Zurück"). The eBook will be deleted from your device and Onleihe account and can be borrowed by other users.