Reading in content in custom page model Problem

The CMS Questions
1

I’ve got a custom page model for storing and retrieving content from a database.

So far I have only used the children() and writeContent() methods, but now I also need a method to read content directly for the respective page. I haven’t found any suitable documentation on how to read content directly for the respective page.

I have tried setContent(), content() and readContent() on a trial & error basis, but only get HTTP Error 500 because of memory exhausted (tried to allocate xx …). Unfortunately these error messages do not bring me any further.

What do I have to do to just fill single fields of the current page by my page model?
Is there a suitable example somewhere that I can use as a guide (which NOT only refers to overwriting the children() method)?

2

More specific:

If I use the content() or setContent() methods, I can return either a new Content() object or a Page::factory() object, and the content from the database will be displayed in the panel page fields. That looks good in the first moment.

But when saving, unfortunately $data in the writeContent() method does not contain the changed content, but the content from the above mentioned methods, i.e. the old content.

So this seems to me to be the wrong way. So I must use neither content() nor setContent(), because that makes writeContent() disfunctional.

But which method do I need to override to fill custom content into the fields of the page?