What should a person who has repented and committed themselves do regarding the prayers and expiations they missed during their period of negligence?

The enquirer has done well by repenting for his negligence in prayer and fasting. The majority of scholars hold the view that missed prayers and fasts must be made up, and this is the more cautious approach. If one is unaware of the number of prayers or days they missed, they should make up what they believe, to the best of their judgment, will absolve their responsibility. As for major sins, we do not know which ones the enquirer committed that would necessitate expiation through fasting or feeding, so we kindly request clarification. Sometimes a Muslim might think that a certain sin requires a specific expiation, when in reality it only requires sincere repentance.