Hi @Katie_Andrews1, welcome to the Asana Community Forum! As it stands, it’s currently not possible to track how long it takes to complete all tasks in a section within the Asana product. As a workaround, you can export your project to CSV and then build a report in Excel or Google Spreadsheets to calculate the time. In the CSV export, we include the creation time and completion time.
You can also find some other tips and upvote for this feature in these threads:
https://forum.asana.com/t/count-the-amount-of-time-between-stages/151438
I hope this helps!