Study technique

Hi sir i was just wondering how to study i am doing 3 papers. But is it better to study (do Pastpapers) 2 subjects per day like p1&p2 or is it better to do only one subject per day like today p1 only then the following day p2 and the day after that the last subject..i am very worried now time is my enemy i feel i have not gotten through enough past papers and i must split my time between these three subjects please help me..also how many questions should i aim to do every day is just one pastpaper for each subject okay or??