How can one atone for multiple sins and transgressions, including adultery, selling work samples, and sexual intercourse during Ramadan? And is fasting on Mondays and Thursdays, along with feeding a thousand needy people, sufficient for sincere repentance?

The major sins you committed, and repentance abrogates what came before it. Indeed, sins can be transformed into good deeds if repentance is sincere and accompanied by faith and righteous actions. Allah says: "Except for those who repent, believe and do righteous work. For them Allah will replace their evil deeds with good deeds. And ever is Allah Forgiving and Merciful." (25:70). And the Prophet, peace and blessings be upon him, said: "The one who repents from a sin is like one who has no sin."

If you engaged in intercourse with your wife during the daytime in Ramadan, you must offer expiation for each day. This expiation is fasting for two consecutive months. If you are unable to do so, then feed sixty poor people for each day. As for the money you took, it must be returned to its owners.