Sorry, for my late reply. It took me longer than expected to intermediately solve the problem. I now changed my plan and do not longer use Microsoft. I am now using my Google account and CalDev for synchronization (I got help of a friend there).
Since I have been using my private Google account, I wanted to switch to my business mail address. This caused a conflict with an another existing YCBM account and now, I am unable to login to q-enthusiast.youcanbook.me.
In the meantime, I deleted the accidentally created calendar [email removed]. Is it possible, to bring q-enthusiast.youcanbook.me to the account under [email removed]?
I did not expect causing further problems by changing the google account mail address.
But I feel, I am getting closer to the end solution
All the best and thanks