A bosom friend means that he can talk, speak his mind and think of everything. He said that he was the first person who thought of anything. This is a bosom friend. How many such friends a person has in his life depends on your luck. If you are lucky and kind, maybe you will have more friends. If you don't meet so many close friends, actually one or two will do. One or two intimate friends can speak freely.
Since we are bosom friends, we should be honest with each other. In fact, I think the most important thing to make friends is sincerity. If you are sincere, others will naturally become this new city. It's not that you have exposed your privacy, but that friends should be sincere, don't play tricks, don't hurt friends, and you are really the kind of person who can talk with each other. Such friends are bosom friends.