The German folk song at the beginning is called "Die Gedanken sind frei" (thoughts are free). The lyrics of the first verse translate to
"Thoughts are free, who can guess them?
They fly by like nocturnal shadows.
No person can know them, no hunter can shoot them
and so it'll always be: Thoughts are free!"
It became a popular protest song against political oppression all through Germany's turbulent 19th century history.
When the stranger places the beetle on the floor (around 45 minutes), the carpet pattern is the same triangle that is on Maura's letter and the captains floorboard/hatch.
The closing song for episode 2 is Child in Time by Deep Purple, sung by Ian Gillan on the band's Deep Purple in Rock album released in 1970.