Hello,
Look, we just disabled third-party plugins, it can’t break your site! Besides to change everything back you just need to enable plugins!
I checked the plugins you are using and see that 500 error on fronend gives JCH Optimize Pro plugin. I have disabled it and everything works fine. If you want to speed up your site you may use W3 Total cache plugin, Autoptimize plugin, read more here https://www.8theme.com/topic/fixing-pagespeed-issues-once-and-for-all-could-apply-to-all-8themes-themes/
Regards
