You can create a new Google account easily if you want one.

https://support.google.com/accounts/answer/27441

If you have difficulty accessing Google sites, please let us know what errors you get.

(If you need access to someone else's Google account, you would need to contact Google to explain why and prove your relationship to the other person. I'm not sure which article is relevant for that, because it doesn't sound like you've set up FamilyLink.)

Note that Firefox 78.15.0 is the last version for your Mac OS X platform (update channel: mozilla-mac-eol-esr1) and you will no longer receive (security) updates.

Current releases require Mac OS X 10.12 or newer.

• https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr

Firefox 78.15.0 on the Mozilla CDN server:

• https://download-installer.cdn.mozilla.net/pub/firefox/releases/78.15.0esr/