Jhn 16:11 Of judgment, because the prince of this world is judged.
[In regard to [their] real mistakes, because, not trusting me neither about justice, because I bring to judgement before my Father, and you no longer observe me], nor about judgment because this social order has been separated.
In the alternative, the two previous verses [in brackets] introduces this one to give us a more complete sentence. Three verses that didn't make much sense, now fit together logically and tie what Christ is saying now to what he has said earlier in a very consistent way. While it is a bit wordy in English, the Greek is clean and easy.
People make mistakes regarding Christ and justice because they live under a certain world order, with its own priorities and values. The world order exists because people believe. They choose it. This means that they cannot believe in its opposite, the word of Christ. The social order and the way of God are always separate. In Hebrew, "separate" means "holy," and the idea is that God and the things of God as separate from worldly things.
So, looking back at these three verses, Christ is saying people make mistakes about Christ for two reasons.
The first of these verses, Jhn 16:9, sets up the fact that people make a mistake.
The next verse, Jhn 16:10, describes the first reason for their mistakes, thinking that Christ is setting himself up as authority for justice when, in truth, he has been given the job of judgment by his Father and those judgments are made before the Father so they are hidden from earthly view.
This verse explains the second category of mistakes: that people reject Christ because they prefer the values of the world.
κόσμον "World" is from kosmos, which mean "order", "good order", "ruler", "world order", "universe," and "the world of men." Matthew uses it when Christ is talking about the order in the universe, specifically the order of the world of men, as it is designed to be.
κέκριται (3rd sg perf ind ) "Is judged" is from krino, which primarily means "to separate", "to put asunder," and "to distinguish." It has a lot of other secondary meanings, including "to pick out", "to choose", "to decide" disputes or accounts, "to win" a battle, "to judge" especially in the sense of "estimate", "to expound," or "to interpret" in a particular way.