Get rid of Norton. It's quite literally useless. And you, unfortunately, bought it thinking you had a malware issue due to fake McAfee notifications.
I assume these are sliding in the from the top right of the screen, which means a site you visited has given itself permission to send push notifications. Everything you're seeing is nothing but a scam.
Open Safari's preferences. Click on the Websites tab and then scroll down to Notifications. Clear any entries in the right hand window. You might find something similar in the Pop-up Windows heading below that. Block any you don't recognize.
Then if you want, uncheck the box on the right, as shown below here.
I personally can't think of any reason why I would ever want any website to push notices to me.
