What is the ruling on exchanging messages between a girl and a foreign young man via phone, and is it permissible for a girl to wait for a specific young man to marry him, even though she is unaware of his social status and his intention behind the messaging, especially since she rejects those who propose to her in comparison to him?

The devil's methods of entrapping a servant vary. You erred by giving your phone number to a non-mahram man and corresponding with him. This leads to the heart becoming attached and the relationship developing into something even more Haram. You have two ways to end this problem: Either propose marriage to him in a way that preserves your dignity, or send him a message informing him that you made a mistake by allowing him to correspond with you, and that you have decided to cut off this correspondence.