How can one make up for past prayers missed over years due to laziness or not performing ghusl after major ritual impurity (janabah)?

Missed prayers must be made up after puberty. According to the majority of scholars, one must first repent to Allah, then make up the missed prayers. If the number of prayers is known, they should be made up. Otherwise, one should make them up based on what is most likely to clear their conscience. Making up prayers is not time-bound and must take precedence over supererogatory prayers, except for some confirmed Sunnah (definition) prayers. As for someone who has missed many prayers, they should make up the prayers of at least two days in one day, unless doing so would harm their ability to provide for their dependents, in which case it is permissible to limit it to making up the prayers of one day.