Hello @mscheidl
Thanks for sharing your assumptions. I agree with you, it seems the configuration fits not exactly. I will reach out to the service provider and start any deep diving on the topic. In case anyone is interested on the outcome I will share the results maybe tweaks.
Yes Dropbox provides also DSGVO compatible Cloud Service in EU - but not for private persons - at least it so expensive that I don’t want to afford that - it’s “only” cloud storage - not more 
Thanks again for support
Have a nice Day
Atze