How do I fix this is currently unable to handle this request http error 500?

Internal server errors (error 500) are often caused by plugin or theme function conflicts, so if you have access to your Dashboard, try deactivating all plugins. If you don’t have access to your admin panel, try manually resetting your plugins (no Dashboard access required).

For More Information Please Refer: https://wordpress.org/support/topic/page-isnt-working-currently-unable-to-handle-this-request-http-error-500/