first of all, your indentation is off.
Secondly, Einleitung is not a section but a field, and you cannot mix sections with field. So that means you have to put this textarea field within a fields section.
If you only use fields, you don’t need the additional sections level. In your case drafts, unlisted and listed are sections (of type pages). Therefore you need to wrap your fields in a section, too (type fields).
The first fields in your example is the identifier of the fields section, this could also be myFields or anything else. The second declares the type of this section and the third lists the included fields.
I agree, this is confusing at first. But once you get used to it, it’s no problem anymore.
Thank you for that explanation! I guessed that the identifier for the section could be another name, but after type: fields - what else could stuff be that comes after that, than …fields? So why can’t it be the names of the fields? Why must there be the - second identifier that says fields?