Generally speaking a 500 error is returned when a server couldn't fulfil a valid request (for many varying reasons). That being the case, I'd recommend talking to your hosting company's support team and check any status pages they may have. It is likely that they are aware of the problem and are working to fix it.
Unless you manage your own server. In that case you need someone with knowledge of linux and apache to dive in there and take a look.
It may be coincidence that you happened to be updating your site at the same time.
Best of luck
Carlos