Part I
Line 5

• 5)  Winter kept us warm, covering
  
• 8)  Summer surprised us, coming over the Starnbergersee
  
• 9)  With a shower of rain; we stopped in the colonnade,
  
• 13)  And when we were children, staying at the archduke's,
  
• 16)  Marie, hold on tight. And down we went.
  

The draft version of the opening line for The Waste Land had another we:

First we had a couple of feelers down at Tom's place.

Who are these groups of people? Are the the same groups?

There are hints that the section containing lines 1 through 18 is made up of 3 sub-sections (1-7, 8-11, 12-18) and possibly 4 sub-sections (1-4, 5-7, 8-11, 12-18).

Note the change in line length between lines 7 and 8.

• 7)  A little life with dried tubers.
  
• 8)  Summer surprised us, coming over the Starnbergersee
  

• 11)  And drank coffee, and talked for an hour.
  
• 12)  Bin gar keine Russin, stamm' aus Litauen, echt deutsch.
  
• 13)  And when we were children, staying at the archduke's,
  

Additionally, there is possibly a difference between thoughts on lines 5-7 and lines 8-11. We might read lines 1-8 as either:

It is a cruel spring now. (1-4)
Winter kept us two warm. (5-7)
Remember that pleasant summer we two spent together. (8-11)

It is a cruel spring now. (1-4)
Winter kept us warm. (5-7)
I'm remembering a pleasant summer I spent with someone. (8-11)