Can I download MacOS Ventura or Sonoma on my MacBook Air 2017?

No, sorry.

Monterey is the most up to date macOS version a 2017 model can run.

You need a 2018 model for Ventura, click here ➜ macOS Ventura is compatible with these computers - Apple Support

and a 2019 model for Sonoma, click here ➜ macOS Sonoma is compatible with these computers - Apple Support

The current version of Firefox will run on Monterey – and Monterey probably will still be eligible to run the latest version of Firefox for some time after Sequoia comes out later this year.

I doubt if you're having trouble with Monterey's version of Safari now, but you could keep Firefox in mind, just in case.

https://www.mozilla.org/en-US/firefox/new/