Fix german translations

[niwla23]

I have fixed some of the errors in the German translations. I did not fix everything but the most important things for a smooth checkout flow, including:

• incorrect translation of "share"
• incorrect translation of "complete payment"
• broken countdown because of template getting broken in auto-translate.
• various unnatural translations

As I am writing this, I just saw there is another pull request but it seems to fix other mistakes.

I am also not sure if the app should use formal (Sie) or informal (Du) language. Right now it is inconsistent.

Checklist

• I have read the contributing guidelines.
• My code is of good quality and follows the coding standards of the project.
• I have tested my changes, and they work as expected.

I did not test the code, just edited the translations online

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[niwla23]

I have read the CLA Document and I hereby sign the CLA

[niwla23]

recheck

[niwla23]

update on formality: In my opinion, it would be best to have a per-event toggle for this in the long run. The preferred way of addressing the audience would vary heavily depending on the type of an event.

[leonv5]

it would be best to have a per-event toggle for this in the long run.

This would be the best way! I was the one, who did the other german translation fix and I had problems to decide what would be the appropriate approach. The easiest way for this formal/informal language toggle could be done simply with two versions of the translation.

[daveearley]

Thank you very much for this!