My WP Website Shows HTTP ERROR 500

For future reference you could use the define( 'WP_DEBUG', true ); at your wp_config to easily spot errors and turn to false when you are done.

Enabling WP_DEBUG will cause all PHP errors, notices and warnings to
be displayed. This is likely to modify the default behaviour of PHP
which only displays fatal errors and/or shows a white screen of death
when errors are reached.

It is not recommended to use WP_DEBUG or the other debug tools on live
sites; they are meant for local testing and staging installs.

More info here