how to update os in imac 2011

Really? What are the 'odds?' Is it that you FEEL 80 or you are ARE about 80 or an OLD soul? This year I've actually started to say I'm 3 years shy of 80...there's just something more profound about 3 years shy of 80 as opposed to just 77 years old...I mean if your lucky enough to live this long. Anyway, this doesn't answer your question. P.Phillips below touched on my concern...potential web browsing issues because of the age of the browser-Safari.

The 'update' page looks 'corrupted'....I'm probably using the wrong term....anyway it's different than what it used to look like and it indicates no updates available. So if I have Firefox, too, will that make a difference? Thanks!

I'm almost 80 years old. Not computer savvy. So what will happen if I can't update the OS anymore?