What is the ruling on forming a relationship with a foreign young man and speaking with him, then sending him immodest pictures, and will repentance from that be accepted?

If you are repentant, remorseful, and determined not to return to sin, then accept whoever you approve of in terms of his religiosity and character, and do not pay attention to the whispers of Satan. For repentance erases what came before it, and Allah accepts repentance and pardons sins.