What is the ruling on the relationship that developed between the questioner and a girl who claimed she was divorced, then they got married ‘urfiyy without witnesses, with the questioner being unaware of the necessity of witnesses in the contract?

For a legitimate Islamic marriage to be valid, the presence of a guardian (wali) and witnesses is required, and a woman cannot marry herself. However, since you married the woman believing the marriage to be valid, this contract protects you from the punishment for fornication (zina) and attributes paternity of any children, if they exist, to you. If you wish to return to her, a new contract must be drawn up through her guardian in the presence of two witnesses, along with the importance of documenting marriage and divorce contracts.