Translate Use Cases section from english to german

[graciousgrey]

Acceptance Criteria:

• Follow the instructions in README.md to set up mkdocs locally on your system
• Translate the file: docs/user-guide/use-cases/flickr.md to german
• Translate the file: docs/user-guide/use-cases/google.md to german

Notes:

• Please do not rename the files
• In case there is a link to a page that is not part of the user guide (e.g. a page from the developer guide) --> link to the english version

[sakshamsingh01]

I would love to work upon it!