What is the ruling of Islamic law on the action of a young man who ends his engagement due to difficult financial circumstances, despite the girl's agreement to wait and endure the circumstances?

A Muslim woman is not permitted to establish a relationship with a foreign man, and you must repent from this relationship. As for the young man's action, if he left off proposing to you due to his financial circumstances, there is no blame upon him, but he must repent from that relationship.