* "Que tu vu" is incorrect: The correct conjugation of the verb "voir" (to see) in the past tense, second person singular is "as vu."
* "fait" is grammatically correct: This means "done" or "made."
* "demain" is grammatically correct: This means "tomorrow."
Possible Meaning and Corrected Sentence:
The phrase likely intended to say something like:
* "What have you done tomorrow?"
However, this is still grammatically incorrect. A better, grammatically correct way to ask this in French would be:
"Qu'est-ce que tu as fait demain ?"
This literally translates to "What have you done tomorrow?", but the intended meaning is: "What are you going to do tomorrow?"