Is falling into masturbation and the preliminaries of adultery after repenting from adultery considered hypocrisy, and should one abandon leading people in prayer in this state? How can one remain steadfast in repentance? And are those who listen to musical instruments and watch TV series considered disobedient believers?

Congratulate the questioner on his remorse and his fear of hypocrisy, for remorse over sin is one of the most important reasons for repentance. He must regret his sin and resolve not to return to disobedience, seek forgiveness, and increase good deeds, for good deeds erase evil deeds. If he returns to sin, he should sincerely repent again, because Allah forgives sins. Among the things that help one remain steadfast in repentance is to recall the ugliness of sin, its danger, and its punishments. As for sins committed in private, they are whisperings from Satan, and one must repent and seek forgiveness for them. There is no harm in leading people in prayer as long as he is determined to repent. Listening to musical instruments is forbidden, and the ruling on TV series depends on their content; one must avoid what is forbidden among them.