What should I do about my past prayers and fasting, knowing that I used to masturbate while ignorant of its prohibition and the necessity of ghusl (ritual bathing) from janabah (state of ritual impurity)?

If you prayed and fasted without performing ghusl (ritual bath) after the emission of mani (sperm) that necessitates ghusl, then according to the majority of scholars, you must make up those prayers. However, some scholars do not obligate making them up if you were unaware of the obligation of ghusl. As for fasting, you are not required to make up the fasts if you were unaware that masturbation invalidates the fast.