The pattern for A.2 is somehow misleading; at least in german. After reading the comments very carefully, I managed though:
It’s important to knit A.2a only once and repeate only the A.2b part.
The boots look a little less sophisticated when made out of cotton yarn, but I think that will be easier for the washing (maschine).
There is a lot of sewing in the end (sides to bottom sole), which I felt was a little annoying and could have been solved by adapting the whole pattern a tad bit.