[AC Question]

Uninstall the app called knox, says system needs to be rooted?

[Rukbat]

True, because Knox is installed as a system app. But the phone will run just fine without all the Knox apps, unless your company requires that you use Knox. (It's a "we're doing something" way of separating company data from your personal data on a single phone. It's about as effective as wishing, but Samsung "did something".) If you don't work for a company that requires it, and you don't mind rooting your phone, freeze or uninstall the Knox stuff.