Currently, you are able to edit your challenge up until it goes live. Once it does so, you'll have to reach out to Litterati to update any parameters (goal, end date, or challenge name.)
There is no way to delete a challenge from the App. However, you can deactivate your challenge from your user Dashboard. To do that you simply sign in to your dashboard from a web browser, click on the Challenges tab, and click on the active toggle on the right of the challenge.
Please note: users who created their account with AppleID, your information has been obscured within our system as part of Apple's effort to uphold privacy and you might not be able to log into the dashboard. Please reach out to firstname.lastname@example.org for more help with your challenge.