What happens when i reset all settings

Reset All Settings Will put your devices Settings back to the default. It will disconnect all WiFi connections so you’ll need to sign back into them. Apple Pay/Wallet may need set up again. You’ll set up Face ID/Touch ID again. You’ll might need to organize your Home Screen layout again.

It does not delete any of your content like Notes, Photos, Contacts, etc. However it is still a good idea to make a current backup before you use Reset All Settings.