What should one do if they have missed many prayers due to laziness or work, and should they perform them with the present obligatory prayer, and how should one pray as the Prophet, may Allah bless him and grant him peace, used to pray?

Neglecting prayer due to laziness or being preoccupied with work is a great sin. Some scholars even hold the view that whoever intentionally misses a single prayer has committed an act of disbelief. The questioner must make up all the missed prayers. If the number is unknown, then he must continue making them up until he is reasonably certain that his obligation has been fulfilled. It is not sufficient to make up one prayer with each obligatory prayer; rather, one must make up as many prayers as possible daily, in order. Some jurists are of the opinion that if there are many missed prayers, one should make up at least two days' worth of prayers per day, as long as it does not negatively impact one's livelihood.