Hello,
Make sure you have checked all the server requirements before the installation – https://www.8theme.com/demo/docs/legenda/Theme_Installation/Legenda_Theme_Requirements.html The 500 error means that there is some Fatal error in PHP script or on the server side. You cna turn on debug mode in WordPress – https://wordpress.org/support/article/debugging-in-wordpress/ to find out what error appears on your site, it will point you in the right direction what needs to be fixed.
Regards
