Destoried Website

Hi i tried to change the front page of a church website, as i am new to wordpress wasnt sure how to do it so was trying a few things.I changed the WordPress Address (URL) by adding /live-3 at the end.
this was suspose to make the live-3 page the home page. but what happened was as soon as i pressed save, i got a Error seen below

“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at 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.”

and now i cant find the word press admin log in, and all the pages are destoried, i have tried increasing the Memory by using Define(WP_Memory_<something>,’64M’); and i have tried everything else that io can find, i have tried doing a restore from the host side, as they take daily back ups but this still hasnt fixed any of the issues.

any advice would be amazing.

The page I need help with: [log in to see the link]