Hello,
I’m sorry but how can we find the reason of your issue if we can’t disable plugins? Especially if problem is caused by third-party plugins. When you provide admin panel details you should understand that we’ll be looking for the reason of problem, will disable/enable plugins and theme to find out what is the problem. If this is not acceptable for you then you need to provide full site archive and DB, so we’ll be able to install a total copy of your site and find problem. But this way is longer.
500 error appears when Loco Translate and JCH Optimize Pro are enabled. Contact plugin developers to sort out this issue.
Regards