how to i update safari for my mac 10.7.5

The only way to update Safari is to upgrade your Mac to El Capitan v10.11.

See if your Mac meets the requirements here > Upgrade to OS X El Capitan - Apple Support

With El Capitan installed your Mac would have Safari 9.1.2 installed. That's the latest version of Safari available.

Browser security is continuously evolving to accommodate Internet threats, and OS X Lion is rapidly becoming an island where Chrome and Firefox support will also cease — sooner than later. At that point, you will be hard pressed to access any online services that expect contemporary browser security support.