How can I be steadfast in prayer and make up for the obligatory prayers I have missed? And do I owe an expiation for my shortcomings in fasting Ramadan and making up the missed days, and what is it?

The first thing a servant will be held accountable for is prayer (Salah), and abandoning it is disbelief (kufr). Whoever establishes it has succeeded, and whoever neglects it has failed. It is obligatory to maintain prayer and repent from abandoning it, and to make up intentionally missed prayers. As for making up the Ramadan fast, it is obligatory, along with making it up, to offer an expiation of feeding a poor person if the delay was without a valid excuse. Sins, however, do not invalidate the fast but rather diminish its reward.