Can I upgrade Safari without changing the OS?

No. The version of Safari you ca run is inexorably linked to the macOS version. You can however, use a different browser like FireFox.

If you are running macOS 10.14 as shown in your equipment line, you will need to get the FireFox ESR version.

https://support.mozilla.org/en-US/kb/download-firefox-extended-support-release-esr-vers?redirect=no

edwardfromnorthport wrote:

can I upgrade safari without changing the OS? can i upgrade only safari without upgrading the OS?

Typically no, you cannot upgrade Safari without an OS upgrade.

Rarely does Apple release stand alone updates for the browser, but as a rule, no.

If you are having trouble connecting to and using websites with your older version of Safari, try it with a newer third party browser that is still being updated to meet current internet security protocols.

I suggest you take a look at Firefox browser or Brave browser.

Download an alternative browser and install it into your Applications folder. Launch and use that when you encounter websites that don't play well with Safari.