What's wrong with "You must not be here"? This version was not accepted.
It means something completely different. Like "You are not allowed to be here."
Thanks! And what should I say to a person who really must not be in some (for example, dangerous) place?
Nesmíš...
Why not "you have not be here"?
This is wrong English syntax. "You do not have to" is how you say one does not have an obligation.