So where is the functionality of "Homepage Einstellungen" to be found now

As written: It was removed.

You have to edit the layout_survey_list.twig file in your extended theme.

Joffm

P.S.
Hättest Du gleich im deutschen Teil geschrieben, wären viele Unklarheiten sicher schneller beseitigt worden.
 

The homepage settings are not relevant for your case, as you want to change the survey list part of the theme.

You will need to access the theme editor and find this file there to edit it.

by the way, this survey list is based on the "base theme" of your installation. The theme you use for your survey can be different.

For changes in this file you need to extend a theme to be able to modify a theme (the standard themes should stay untouched), and then you need to set this extended theme with your modifications as your base theme.