Thanks for the question.
In general, you must mark work orders "Closed", unassign or delete the Project in Pruavan Online to have the Project drop from Pruvan Mobile.
Pruvan Mobile keeps Completed Project's on the device in the event that more work needs to be done in the field.
Since Pruvan Mobile is an offline/online app, we must allow folks who accidentally Complete a Project in the field to continue to take photos in the event they see a need to take more photos.
If you are using an Integration, your work provider may or may not send Pruvan a "Delete" or "Closed" signal. You can also perform a "Full Import" which, depending on the Integration, may remove Projects that are no longer in the work order feed sent to Pruvan.
You can always delete Projects in Pruvan Online. This will not delete related photos or field results searchable on the Pruvan Online->Photo Tab.