Hi Holger,
For:
1. The layout switches to mobile layout with different layout of left panel navigation at a threshold of 1200px.
Response: We have reduced the responsive break point for tablets to 1000px. This will be in our next release (3.1.1) due out before the end of this month.
2. The hamburg button in the top left of the mobile layout opens a grey pannel with only "Contents" shown there. Instead it should directly show one level deeper like in non-mobile layout Release Overview, Getting started and all the other first level chapters of the documentation
Response: It is not possible to have the contents automatically visible in the responsive output due to a limitation in the tool we use to generate the help documentation. We have submitted a feature request for this.
Thanks,
Catharine