upadate my firefox for my macbook air

Hi, you have the last version of Firefox for MacOS 10.11. We don't support this OS version anymore.

If you can upgrade to macOS 10.12, 10.13, 10.14 then you can run the still being updated Firefox 115 ESR.

Firefox 116.0 to current requires macOS 10.15 (ten.fifteen) or later to run.