How can we use 做 in this meaning in other sentences? Where can I read more about it and what is the name of this "rule"?
And what is the meaning of the 了 in this sentence?
做 + identity = be identity
Example:做好人，做首領 (good person and leader are identities)
做 + procedure/action = do procedure
Example: 做大事， 做錯，做工 (great thing, mistake and work involve procedures or action)
the final particle 了 is a modal word for emphasis, if you remove it, the meaning of the sentence would not change, but the tone would be flat
"要(做)大人物就要(做)大事" = "to (be) a great man, you need to (do) great thing"
Why do we use 做 in this sentence as “being”?
朋友 is an identity
Well, whereas in English you 'be a friend,' in Chinese you '做朋友。‘ Not much of a rule. Why does that surprise you? Do you think Chinese must copy English?
Have a look here. Number 8
You could write:
Edit: I was reading an interview with a TV presenter today. He was asked if he acts role of an intellectual in his TV show. He said:
I think there may be a similar form in English.
A: You should try to be more friendly.
B: I don't do friendly!
What is the meaning of 了? That is a whole Pandora's Box of questions!
The simplest answer is, it makes the sentence sound complete. Otherwise it sounds strange, according to a Chinese friend.