Translation:You are not having lunch where János is having lunch.
WHY isn't "You are not having lunch where János is having lunch" accepted? Why on earth are we supposed to translate the name into John??
You really shouldn't be. Please report it next time, if you haven't already.
Is it possible for this to be "with Janos" instead of "where Janos is having lunch"?
No, not really, since you can say "nem Jánossal ebédelsz" in Hungarian as well.