I found your solution in GitHub for this kind of Problem: adding the line: charset = utf8 in the database section of config.ini.php.
I did this as well and the websites all came back in the administration.
But when I now look at my data the page titels are not displayed correct and look like this:
Broschüren --> should be: Broschüren
Spaßbäder --> should be: Spaßbäder
The database is utf-8 and the pages are all utf-8 as well.
What can I do?
Best regards
Christoph