German translation update

[krsilas]

This PR includes three changes:

• Improvements for wordings that I either found grammatically incorrect, inconsistent or just could be phrased better.
• The dialog for creating tasks had some text hardcoded. I made them dynamic and added german translations. In other languages it will still fall back to english until someone will add the new translation entries.
• Controversal take: I renamed "Beschriftungen" back to "Labels". While "Beschriftungen" is the correct translation for physical labels, that naming has never gained any widespread adaption in the software world. And "Labels" is a very common anglicism. All examples I could find used "labels" or "tags" in their interface.