What are the obligations and duties incumbent upon a person who has spent his life in sin, neglecting prayer and fasting, committing forbidden acts, and stealing money, and how can he repent and return to Allah, and what should he do about the stolen money?

Start your year with sincere repentance and stay away from what is unlawful. Seek help through marriage, reading books of encouragement, voluntary fasting, filling your time [productively], associating with good people, and observing prayers regularly. You must make up for any missed fasts, along with an expiation of feeding one poor person for each fast you delayed until the next Ramadan (definition). As for prayer, there is a difference of opinion regarding the obligation of making it up. You must return people's money or seek their forgiveness. If you fear exposure, return it under any guise, such as gifts.