Not getting any notifications on iPhone 8 Plus

Do not disturb is not activated.

Well, it happened 2 weeks ago. First couldn’t lock screen when I pressed the volume down button.. volume went right down to 0 after I pressed once. With assistive touch I can lower the volume by one and then switch off the screen with lock button.. then I noticed I don’t get any notifications. I’m not sure why...first I the resettled settings. Didn’t work... reset the phone with iCloud backup didn’t work. Still didn’t receive notifications. Well, then I did a test. A friend of mine sent me a message over what’s app. It only had one mark beside the message on her phone. Meaning the message was not even received on my phone... I opened what’s app and then all messages came in. I always have to check all apps if there is news... occasionally it notifications work but only 1 every 2 days.. so very Seldom... it is very strange and I don’t know what to do.

The same question was asked here but frozen