You may want to check how your notifications are set up: eg: in accordance with Apple's methods.
ie: Browse through the info. in: Change notification settings on iPhone - Apple Support
Eg: says:
"Most notification settings can be customized for each app. You can turn app notifications on or off, have notifications play a sound, choose how and where you want app notifications to appear when your device is
unlocked, and more".
and
"Receive Web Push notifications from web apps
You can receive standard Web Push notifications from a web app
when you add its website icon to your Home Screen.
Web Push notifications can keep you informed of activity in the app. After you subscribe for push notifications within the web app, the app can send you notification alerts and badges similar to the ones you get from other apps on your iPhone".