*anonymous user* Thanks for reaching out!! To monitor Azure Data Factory activity runs , I would suggest you to enable diagnostic logs to log the data in log analytics workspace related to ADFActivityRun, ADFPipelineRun and ADFTriggerRun. After enabling the logs, you can query the log analytics workspace to get the time taken for each activity run.
Sample Kusto example to time taken for activity runs if the destination table is selected as Resource-specific
ADFPipelineRun
| extend timetaken = End - Start
| where Status in ('Succeeded','Failed')
| project TimeGenerated , OperationName , Status , timetaken
For more information on how to monitor azure data factory with Azure Monitor , kindly refer this document. To learn more on how to write kusto queries, kindly refer to this documentation.
Hope this helps!!