If I have a 24 inch iMac 2009 and my web browser is outdated what can I do

Of the browsers listed, only Brave still supports macOS 10.11.

Brave:

Chrome:

Vivaldi:

FireFox:

El Capitan is it and you should consider replacing the iMac.

Until then, you can try FireFox, Vivaldi, Brave or perhaps Chrome.

It’s not just obsolete, it’s insecure as well. Recycle ASAP (free at any Apple Store) and replace.