There is a huge cultural difference between Sweden and the country you live in, so maybe it is difficult for me to give you a good answer. In Sweden, people get married only if they really want to, and their parents have nothing to do with their decision.
Our Dutch specialists have written about how to deal with early/premature ejaculation. There are various treatments to solve this problem.
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About penis size, it seems that your friend is worrying unnecessarily. Most women care much more about other things than the size of a man's penis. It is more important to be able to make a woman happy, rather than having a large penis
(Read about how to make a woman happy), -
(Read about how to make a woman want you).
If you live in a culture with arranged marriages, where the bride is virgin until the wedding night, then the woman does not have much to compare her experience with. Men believe that women have a fixation on penises, as many men have, but most women appreciate much more other parts of a man's body and his personality.
The low sperm quantity depends on the fact that your friend masturbates often. With the course of time, he will probably calm down a bit, and his body will manage to produce more sperm. I don't think that his penis has become smaller; masturbation does not cause the penis to shrink. It is most likely that his body has become bigger since he was 13 years old, so that is why his penis looks smaller.
Young boys have a very strong sexual drive and often do not have any chance to have intercourse. That is why there is no other way to have sexual release other than masturbation. As time goes by, this strong drive decreases.