I need content with the server operation "Set properties for an object"

I assume it is a creation of a new non-document object.

Another operation that takes ages to finish: "Create a single-file document"  (more than 46 seconds). Any idea what might be the reason?

If you see a lot of these then it could be indicative of a performance bottleneck.  This is probably quite difficult to diagnose via a forum, but you may want to reach out to your partner support team and see whether they have any advice.

Hi,

we found a reason. EventHandler it is

Yeah, code is often the reason for delays like this (although 46s is huge, so I'm not sure what's going on there).  Glad you found it!