Internal Server Error after changing the site in setting

Hi there, I cannot connect to my site: https://www.themarketingtrendz.com/ after I change the site into https://www.themarketingtrendz.com/en/ in Setting – General. It showed: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator at (email redacted) to inform them of the time this error occurred, and the actions you performed just before this error. More information about this error may be available in the server error log. Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request. Could anyone help me to change the site back to my website in Setting? thank you a lot!