It is obligatory to make up, means to perform the Qadha, of every
missed obligatory prayer. The easiest way to perform all the Qadha prayers if the
period is long, is to perform only the Wajib parts of the Salaah. Only
the Wajib parts of the Salaah with out the recommended parts will make the Qadha easier. And it is good to make a timetable every day and night to spend some time in
performing of the Qadha and that also will make it easy Insha Allah.