Definitely a glider, as indicated by the yellow tow release handle and the wings of the one in front.
Back seat of an open-class two seater. As the ASH-25 is out because of the split canopy, one would say Schemp-Hirth Nimbus 4D
Is the disconnected monocycle "thingy" in the top left of the picture of any relevance to the subject aircraft.
It's a trolley wheel used for ground handling