Zend certified PHP/Magento developer

Running php bin/magento setup:upgrade caused magento 2 app to crash

I originally was facing an issue of not being able to save any configurations on my magento application, and a user on this site recommended to run the php bin/magento setup:upgrade command as the first step to resolving my issue.

Well, that only created a much larger issue. When running the command, I got the following as an error:

Class MagentoFrameworkAppConfigFileResolverProxy does not exist

Also, now my magento application is completely crashed and I am unable to access it from the browser. When trying to access from the browser (whether it be the admin site or the user facing site), I get the following error:

An error has happened during application run. See exception log for details.

I am really just looking to get my application back up and running. Does anyone know how I can possibly revert the actions of running the upgrade command or somehow restart the application?