Hello,
I was able to fix the problem with your instructions and thus avoided another disaster recovery. I went for the first one “Lazy and easy”, was the easier way for me and worked fine. Thanks for the link to the tutorial.
A blackout during a disaster recovery would be terrible of course, I hadn’t even thought of that during my first restore. 
It does not belong in this thread, but I would still like to thank you for your many contributions, I have already drawn good tips from it. I have adjusted my DNS settings, for example, after a contribution from you. 
Erwin