Either this means someone is dead, or it's another of those dreaded partial sentence translations. "You are not in this world - to teach others what to do."
This is a nonsense phrase in english.
Similar phrases that do have meaning, but I don't know if any of them fit:
you are not of this world / you are too good for this world (for someone who's so kind / giving / moral that they get taken advantage of)
You're out of this world (you're great, groovy--this is a bit 1960's-1970's)
Your head is in the clouds (you're not paying attention)
You are not well grounded (you or your arguments lack a sense of reality or a basis in reality)
It's nonsense in Portuguese either! I could infer 'You're out of reality' or 'You're not well grounded' as you wrote...
English equivalent idiom: "You're on another planet"
Meaning: Your ideas are ridiculous.
I don't know... but we use "você está no mundo da Lua" when someone is not paying attention to you.