Is it advisable to marry a girl with whom one previously had a relationship, when both have repented and desire righteousness? And will the sins of this relationship be transformed into good deeds by marrying her?

One must hasten to sincere repentance from sinful relationships, which are a gateway for Satan to the soul, leading it to fornication and indecencies, as Allah Almighty says: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing." If the girl repents, then marriage to her is among the best guidance for the two lovers. However, if fornication has occurred, then repentance and purification are obligatory, and it is permissible to marry someone else, whether she has repented or not. It is hoped for whoever repents with sincere repentance that Allah will replace his evil deeds with good deeds, as Allah Almighty says: "Except for those who repent, believe and do righteous deeds. For them Allah will change their evil deeds into good ones. And Allah is ever Forgiving and Merciful."