"I am not allowed to eat."
Translation:Απαγορεύεται να τρώω.
Απαγορεύεται is an impersonal verb. The phrase literally means "it is forbidden that I eat", where it has been dropped from the Greek sentence, and that I eat/να τρώω is the verb's subject.
I'd say that "I am not allowed to eat" would be translated a bit more accurately as "Δεν (μου) επιτρέπεται να τρώω". Επιτρέπεται is still impersonal, but at least the sentence keeps the allow and the negation.
If you were to see this sentence out in the wild (say, on a metro car where it is forbidden to eat) would this be how it os written? Would you conjugate the eat in first person, or maybe second (να τρως)?
You'd most often see the noun "κατανάλωση"=consumption.
It would be something like:
Απαγορεύεται η κατανάλωση φαγητών/τροφίμων και ποτών/αναψυκτικών=(lit.) The consumption of food and drink/beverage is forbidden. ;)
Does πρέπει να φύγω fall into the same sentence structure? It is a must that o go?