As someone who checks my own phone constantly, I realize how important the phone working at the proper speed can be. Let’s get your device back up to speed. What type of phone do you have? To clarify, what type of update was this (software update, application update, etc.)?
after any update you need to check everything, notifications, ring-tone, dnd settings, sound, etc.
you may now have every app providing notifications....settings/notifications/advanced, select those you want notifications from.
fwiw: my ring-tone has changed several times...i just change it back.