User Guide: Headlines in german Translation are in English

[christf]

Issue: Bug report

While the content of the user guide is properly translated, the links are not.

To Reproduce 📃

Viewing the index page on https://docs.erpnext.com/docs/user/manual/de displays that all the overview pages are in english rather than german.

Expected behavior 📈
The page links should be translated too

OS (please complete the following information): 🌀

all

Possible Solution 📑
Translate the index pages