Must I repeat the fast of Ramadan because I performed ghusl from menstruation without washing my hair, due to my ignorance, at the age of fifteen? And am I considered sinful for that?

The obligatory ghusl (definition), such as that for menstruation and janabah (definition), requires covering the entire body with water and ensuring it reaches the roots of the hair, by agreement of the jurists. Wiping is not sufficient. It is not obligatory to undo braided hair; rather, it is sufficient for the woman to pour three handfuls of water over her head and then pour water over the rest of her body. Missed prayers for which the ghusl was not performed correctly must be made up, noting that ghusl from menstruation or janabah is not a condition for the validity of fasting.