Quick sex

Just started having sex with a guy I’ve been talking to for almost a year. Last week was the first time we had sex but he told me he haven’t had sex in almost a year (a week before we met or so) which could be true..anyways we had sex for the first time and he nut within 5 seconds tops. Then we had sex yesterday and this time it was maybe for 30 seconds. I don’t judge. I’ll eventually say something to him some way some how but Any suggestions for longer sex? Any suggestions at all? Why is this the reason?