Description and Steps
How to fix HTTP error 500?
You should upgrade your server PHP to version 7 or at least 5.6
WordPress recommended PHP 7.2, You can read here:
Also increase your server PHP memory limit to 128M
If you can’t do it, Contact with your server support and ask for upgrading your PHP to version 7 or above and PHP memory limit to 128M
Still need help? – If still can’t see your website and getting error 500, you can contact with your server support.