Hi so I'm 17 years old, never had sex but masturbate. After watching pornography I see mens penis foreskin drop and can pull it right back, I struggle doing this and have always wanted to especially to clean my foreskin. When I masturbate my skin comes back but only as far as it will strech like towards the head of penis. I'd say hard my penis is roughly 12-15 cm. I hope this is good information
Try using a lubricant on your penis and slowly try to slide your foreskin down the head. Do not get rough or go down fully all at once, if it is still tight. Over a period of days, if necessary, slowly stretch your foreskin.