Is it obligatory to make up the days that I broke my fast in Ramadan due to masturbation, knowing that there is doubt about prior knowledge that it is among the things that invalidate the fast?

Masturbation is forbidden, and if you were unaware of its prohibition, then according to the more sound opinion, there is no sin upon you. However, if you knew of its prohibition but were ignorant that it invalidates the fast, then you must make up the days on which you practiced it, provided you are certain you had reached puberty at that time. Otherwise, there is no make-up upon you. It (masturbation) does not invalidate the fast unless semen is discharged.