How to work with the former
Whatever the reason for your parting, but you should stay with your former if not friends, then at least in normal friendly relations. And you and your former young man must understand that if you become enemies for each other, then it will be difficult for you to work together. At first, it is quite possible to limit your communication only by working moments and questions. Staying in good relationships does not mean at all that all breaks for lunch you must spend together.