Thank you very much! I'm getting a bit further now.
Although sfc and dism are finishing without error now, I am now still unable to install the latest Windows Updates.
Update KB4537762 is offered through Windows Update, but it fails with error "0x8007371b". I have downloaded the standalone package from the WU Catalog, but this one also doesn't complete yet.
Please find fresh CBS logs in the attachments. Thanks!