Hi,

To update Firefox to the the latest version, please check out Update Firefox to the latest release

The web whatsapp site requires Firefox 115.0 at minimum unless that changed recently. You appear to be running the older Firefox 113.0.2

The Firefox 113.0.2 version leads me to think you are running a older version of Mint or Ubuntu and it is no longer getting software packages updates due to being EOL in support.

So you need to update your Linux distro to a current supported version or use the Linux Firefox tarball from Mozilla to use current Firefox versions with internal Firefox updates from Mozilla.