Is a young man who masturbated during a Ramadan day due to jinn possession, then completed the act due to continued lust, considered to have broken his fast intentionally, and how can he rid himself of the intense and persistent lust?

First, we advise you to perform Ruqyah and engage in the remembrance of Allah Almighty, as this is beneficial for ailments of the soul and body, and it repels Satan. If you masturbated during a Ramadan day and semen was ejaculated by your choice, then your fast is invalid, and you must make up that day. As for getting rid of lust, the best way is marriage. Otherwise, fast frequently as a supererogatory act, adhere to the remembrance of Allah Almighty, associate with the righteous, stay away from provocations, and occupy yourself with what benefits you.