I have no experience with the camera, but my quess is that the button with the red arrow and the R is the rewind button. Hold it in the direction of the arrow while you rewind the film. The film advance mechanism looks like it needs a removable takeup spool similar to those used on the old Leicas. If your co-worker did not give you one with the camera you may be able to fabricate one out of the spool from a 35 mm film cartridge.