[python/de] Overhaul German translation

[michi-onl]

This PR overhauls the complete German translation of the Python tutorial for Learn X in Y minutes. The translation covers all sections that are currently available in the English version.

All code comments and examples have been translated while preserving the original code logic and output.

• I solemnly swear that this is all original content of which I am the original author
• Pull request title is prepended with [language/lang-code] (example [python/fr] for Python in French or [java] for multiple Java translations)
• Pull request touches only one file (or a set of logically related files with similar changes made)
• Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md

[Menelion]

@michi-onl Vielen Dank!