How do I uninstall safari?

As it is an integral part of the macOS, Safari cannot be uninstalled.

Please see:

Stop unwanted Notifications - Apple Community

Also:

Block pop-up ads and windows in Safari - Apple Support

Turn off notifications for an app or website on Mac - Apple Support

In addition to the D.I Johnson reply above, Safari can’t be deleted and Safari is also protected against corruptions and malicious activity. You can’t remove it, and removal wouldn’t help. Things have changed in security in recent years.

Somewhere along the path, you were offered and accepted website notifications. You no longer wish to receive those notifications, and can follow that first link to both disable those notifications and to prevent any future website requests to send you notifications.

There is also no need to re-install macOS here. And restoring macOS should preserve these notifications, too. Which is not what you want to do here.

Not possible, unfortunately. Reinstall macOS instead, see What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

Be careful to backup and restore only files that are user data files i.e. documents, videos, music & images i.e. manually without using Time Machine.