1. In normal conversation, Americans ask us to take notes and say write them down. Or take notes. I usually don't say it when I write it down.

Making friends is making friends (plural, so you are right)

You can understand the context of making friends: shall we make friends? I want to make friends with XXXX.

I want to make a new friend. -actually, making a friend can write a deal with a friend. . .

3. Humans generally refer to humans, humans and so on. Generally, I will replace humans with humans.

People actually mean people. There are more people. Like the People's Square in Shanghai: People's Square.

Person, usually used to refer to/refer to someone. . For example, a person with long hair is terrible. Well, I made this sentence up. It doesn't matter if you think it's not awesome to have long hair. . In fact, if you use person, you mean someone. I have never seen the plural of person, because it will be directly replaced by people.