Thanks jdo_apple for your answer.
The problem started after installalation of OS 11.2.2. In spite of a good internet connection my Mac tells me that a problem exists with the connection to iCloud. Finder is not responding all the time and needs to be often restarted. In Apps that uses iCloud, I had to change the options in iCloud drive. I had to uncheck the desktop & documents, because it was not possible to use them on my mac. Dragging a file to another spot was impossible and opening a file in the map desktop or icloud drive was a too lenghty process. Most of the time (not always) I then get error code -36.
In finder opening a file in the icloudrive gives me a minute or more of beachballing.
Thanks for helping