Is it obligatory to make up the days of fasting during which I practiced masturbation in Ramadan unintentionally or without excessive desire, and I sometimes performed ghusl before prayer; and are my fasting and prayer on those days invalid?

If you are not certain that semen was discharged, then your fasting and prayer are valid. Masturbation does not invalidate the fast nor necessitate ghusl (definition) (ritual bath) unless it results in the discharge of semen. Assuming that semen was discharged out of ignorance that it invalidates the fast, then the more likely opinion is that your fast is not invalidated. In any case, you are not required to make up the fast or the prayer. Performing ghusl when semen has not been discharged is sufficient if it includes washing the limbs of wudu’ (ablution) in the prescribed order, and with the intention of removing ritual impurity or permitting prayer. Even if you neglected the prescribed order, then your purification is valid according to some scholars, and there is no blame on you in adhering to the less preferred opinion after the action has occurred and making amends is difficult.