Hi @Hagen,
I can only help you in English, but I read your question with the help of Google translate, so I think I know at least the general gist of your question.
Please see
https://forum.manjaro.org/t/root-tip-use-systemd-to-mount-any-device
followed by
https://forum.manjaro.org/t/root-tip-systemd-mount-unit-samples
I believe those will be of great benefit to you.
Hope it helps!