Peace be upon you.
Ayatollah Khamenei (may Allah protect him):
You must make up for every prayer that you are certain you performed while in a state of major impurity (janabah) without a proper ghusl. As for fasting, if you engaged in this act while fasting and were aware that it invalidates the fast, then you must make up the fast and also provide a compensatory act (kaffarah). If you were unaware of its invalidating nature but knew it was forbidden, then in addition to making up the fast, you must also provide a compensatory act as a precaution. If you were unaware of its prohibition—like in your case—you only need to make up the fast. Regarding the days that followed, if you were ignorant of the issue of janabah or were certain that fasting remains valid while in a state of janabah, you do not need to make it up, and your fast is considered valid. However, it is advisable to make it up in the latter case. If you were aware of the issue of janabah but were uncertain about the obligation of ghusl, you should make up those days as a precaution; otherwise, you must make up the fast and provide a compensatory act together.
Ayatollah Sistani (may Allah protect him):
You must make up for the prayers you performed after becoming impure until the first valid ghusl you performed, whether it was obligatory or recommended, such as the ghusl of Friday. If you are unsure about the number of those prayers, it suffices to make up the certain ones, meaning the least number. You do not need to make up the fast if you were ignorant of the ruling and were excused for your ignorance.
May you be successful in all good.