Hi,
I see that you have a 500 HTTP error when you click on a menu item on your website.
This indicates that there is a fatal error happening. But it doesn't say where.
We would need the full error message to be able to help.
There two things you can do:
1. Activate the "error reporting" and "debug mode" settings of the Joomla configuration and access a page with that error again and see if you get more information about the error. If so, please provide a screenshot of the additional information.
2. Open the PHP error log of your server and look for the "fatal error" message which correspond to that issue. You should get one such error logged for each time someone displayed a page with that error, so you should find many of them.
The full error message should contain the file path and the line in that file where the error happened. Please provide that information.