If you want to delete previous GPS sessions, please go to Home page (the shoe icon) -> Profile (tap avatar on the top left) -> Activity & Log History -> find the entry you wish to delete -> swipe left the entry -> Delete
Please note that once a session is deleted, the activity data including steps, distance and calorie counts will also be deleted. If you have shared the activity to your Feed, deleting the activity will delete the post too. All likes and comments will also be lost.