A message with a lot of content. Thank you! I’ll try to answer it adequately.
Blockquote
there’s no separate contacts / addressbook in Android itself. It’s all abstractions and the contacts app itself is a query / insertion client. Apps can interface with that provider or roll their own databases
According to the explanation, is this “Kontakte” entry a product of (in my case) Whatsapp? Or vice versa?
I have made an attempt. I created a test entry in the contacts and only there… The entry is not transferred to the address book. But the reverse is true. Every entry in the address book appears in the contacts.
Then I would like to change the name of the address book, but that’s just a side note.
I would like to delete this entry from the “enemy” Google, 
but apparently I can’t…
Basically, I am open to tools with which I can “look” into the program.
However, my interest only goes as far as I can actively improve something for myself. I’m not interested in just looking at the technology. I’m just an end user.
Apparently you don’t use the address book function. How exactly do you do that then?