What should I do for God to accept my repentance, and for my family not to be afflicted by my sins after I committed the sin of adultery while I was married, and is it possible to perform Umrah on behalf of the guardian of the woman with whom I committed adultery?

Adultery is one of the gravest sins. Allah Almighty has associated it with polytheism and unlawful killing, and has described its perpetrator as one whose torment will be multiplied and in which he will abide in humiliation, especially if the perpetrator was married. However, the door of repentance is open, and Allah's pardon is greater. Whoever repents, Allah accepts his repentance. For the sincere penitent, his evil deeds are transformed into good deeds, and Allah forgives all sins. The conditions for sincere repentance are: abandoning the sin, regretting having committed it, and a firm resolve not to return to it. One must increase in seeking forgiveness and performing righteous deeds such as Hajj, Umrah, and prayer; for indeed, good deeds obliterate evil deeds. All sinful relationships and introductions to disobedience must be severed. As for the other party in adultery, if they were adult and willing, they have no right over you, nor does their guardian.