If you no longer need the help you requested in the app, you can easily delete the request. If you want to edit the request you can follow the same steps.
Launch the app and click "Home" in the top-left corner
Click "Your requests"
Click on the request. Make sure you click directly on the text, not on your name or the group in which you posted
Click on the three blue dots in the upper-right corner
Click "Delete your request"
Your request is now deleted and will not be visible for anyone
If you want to edit the request, simply click "Edit" instead of "Delete". When you have made the adjustment, click "Update" and the changes will be automatically saved.