"I am having lunch between the bank and the hotel."
Translation:A bank és a szálloda között ebédelek.
It needs to be a hotel, not az.
By inserting the pronoun én right before the verb, you are putting the focus on "I" in a pretty strong way so that the meaning is closer to, "It is I who am having lunch between the bank and the hotel." That's not wrong, as long as that's what you mean, but it's probably more likely that you're using the sentence to tell the listener where you are having lunch, rather than who is having lunch there.