If you have an iOS smartphone:
Open your phone's "Settings" app (not the Formyfit app)
Tap on [your name]
Tap on "Subscriptions"
Tap on the subscription you want to manage (Formyfit)
Tap on "Cancel Subscription"
If you have an Android smartphone:
Open the Play Store
Tap on your profile picture in the top right corner
Tap on "Payments & Subscriptions"
Tap on "Subscriptions"
Manage your subscription using the available options