Hi @CDoelling
It is possible yes to make tracking like that however the answer changes depending on the version of Nintex/Forms/SharePoint you are using.
For form filling tracking you can simply add a calculated field (older forms designers) to track when the form loads by setting the value to current date/time if it is not filled.
For newer forms you would use a variable to essentially do the same and store it in a control.
Once the workflow runs then one of the form field values will be a date/time containing when the form was opened and you can then compare that to the date created field to get the form edit time.
Tracking and storing that is entirely up to you, beacons can be used to store the data back into Nintex Analytics from that point if you like or you can store it into the SP list and tie that to PowerBI.
Jake