Open Settings
Tap Notifications
Turn off Allow Notifications for the app you want
Or tap the app and turn off Sounds, Badges, and Alerts
To stop all notifications, turn on Do Not Disturb or Focus
To silence notifications temporarily, use the Focus button in Control Center
To turn off notification previews, tap Show Previews and choose Never
To disable lock screen notifications, turn off Lock Screen under Alerts
To disable notification badges, turn off Badges
To disable notification sounds, turn off Sounds