Questions & Answers about אפשר להיכנס?
אפשר means possible, can, or is it possible in this kind of sentence.
להיכנס is the infinitive to enter / to go in.
So the structure is literally Is it possible to enter?, even though the natural English meaning is May I come in?
Hebrew often uses an impersonal structure here.
Instead of saying Can I enter?, Hebrew very naturally says אפשר + infinitive, which is more like Is it possible to enter? The person is understood from the situation.
So even without אני (I), the sentence can still mean May I come in?