The first time is really easy to cum, thus you need to be slowly at first until you can fully control yourself, don't focus on the girl and think something else will help you to pass the most sensitive period, then you can do it as you wish.
For me, the first time I normally cum in 10-15 mins, but recently I found I can last longer if I wanna fully control. Btw I'm an extremely guy and I do not prefer being slowly, I mean do with my fastest speed for 10-15 mins without having a break, that really make lots of fun.
The second time I can go last up to 30 mins, fastest speed too. And usually the second time people tend to maintain longer (normally 5-15 mins), as I mentioned above, do some mind discretion, think about others like news, stock price, markets etc. which will boots your performance.
Btw, maintain your physical exercise, running is highly recommended. I run 5 miles every day, which significantly improved my body. And do not masturbate often, that will make you soft and weak, cum quicker and get a erection problem.
Good Luck