It may be a bit too frank for a 15 year old, but a 21 year old could learn a thing or two from it that will last the rest of his life and benefit his partner someday.
Good luck.
Hello there,
I think Kevin has a good point over there and that there is a way to increase your performance. Of course I believe that this requires certain exercise. First of all I believe that you will have full support of your girlfriend because she will want to participate in something that is going to help her to enjoy longer.
So first masturbate two or even three times before you have sex, for example if you are going out and you are sure that afterwards you are going to have sex masturbate and you will see the changes. also you can try this old trick. Take him out second before you come and calm down and then continue. I hope this will help.
Some guys apply penis health cremes in an effort to desensitize the area. The theory is that during the daily application process, you will be introducing your penis to new textures and sensations, which should lessen sensitivity. You might want to try this out. Good luck.
if you cant sugess good then do not give improper advise.