Add a datetime-variable ‘StartedThisNanoflowAt’ to beginning of your nanoflow and log the duration of each activity.
with this in the logmessage(s):
toString(millisecondsBetween([%CurrentDateTime%],$StartedThisNanoflowAt))
If you want us to help you find the time-inefficient activities in your specific nanoflow, add more information on it, like a screenshot.