Many thanks for the reference. I am trying to understand this as a whole and also came across this page:

https://learnmeabitcoin.com/technical/script/p2wpkh/

I hope the explanations there are correct.

I think my difficulties in understanding are due to the fact that I have not yet understood the classic P2PKH procedure in detail. So I still need to study it myself.

One question that is bothering me: What exactly is signed with the P2WPKH procedure? I sign on my offline wallet with the private key material. But what is the input for a signature?

Or to put it another way: How does the Core Client check the correctness of the signature? To which data does the core client (or another Bitcoin programme) apply the coresponding pubkey?