When?/where?

Season - I imagine the season to be autumn, I thought this immediately from the front cover of the book as the colours are yellow, oranges and reds.  Also, in the opening paragraphs of the book the line "Young men are calling their girls. Standing out in the cold.." This suggests it isn't summer as the evenings would still be warm.

I found this painting by Stefan Kuhn of Berlin in 1925.  The trees are autumn leaves and the women still look somewhat classy in their fur coats even though everyone is struggling for money.

Fräulein Kost has just led one of her customers to the door. I think this suggests they have just slept together, although she claims that she only ever plays music and eats chocolate.  I think she says this so people do not get the wrong impression of her, when she secretly uses prostition to earn her money.