HTTP 500 or Internal Server Error is one of the most common errors that blog users, especially beginners put in panic. If this happens to your site, don’t panic, relax, take a deep breath and I’m sure if you read this post, you’ll get your site running in no time.
But before we do that, let’s understand what is HTTP 500. HTTP 500 or Internal Server Error does not just happen to your site, but in the server you are at as well. It is one of the least helpful error because it won’t explain what brought you the error and what are its possible fix. There are severl possibilities that this happened to your site. These are:
PHP memory limit.
Corrupted .htaccess file
when trying to access the administrator area
Here are some fixes you can do: http://www.wpbeginner.com/wp-tutorials/how-to-fix-the-internal-server-error-in-wordpress/