Let’s have a little photo quiz in between:
What is this on the photo?
Alright, it’s pretty clear that something is being reflected in the water, as is which lake this is… so the more concrete question:
What is reflected in the water?
Solved by David: The yellow stripes that are reflected here prevent the boat (on the left) from being shit on by birds like the boat on the right:
What’s this detail from?
Solved by, well, rather all three participants together: David, Julia and Konna:
An artistically painted tram/streetcar, the Rizzibahn in Heilbronn:
Thanks for participating! 
What’s this detail from?
Solution by Dee: A crane (more specifically, the top of the jib):
What’s this detail from?
Solved by m.o.m.: the head rest of a train seat in the München-Nürnberg-Express (RE 4011) – which I didn’t want to hear that exactly, of course. 
Thanks for participating!
What’s this detail from?
The solution, found by Konna:
An old bincular:
more content in German | mehr Inhalt auf deutsch