How to delete activity data?
Go to Activities widget in the watch and finds all activities history➡tap the activity you want to delete ➡ swipe up to the end of the page and you will see delete button.
Delete from Amazfit App:
Amazfit App➡ Workout/Status➡Click See more exercises ➡press and hold the activity you want to delete till the dialog Delete this record pop up➡ click OK button to delete it.
Note: Once the data in the App is deleted, there is no way to retrieve it from the Cloud or anywhere.