"many years ago one tried to grow a tree.but the tree finally died even treated very well by him ,but the other day,he put a seed into the soil,and several years later,the seed becomes a tree"


if we want to find something/get someting ,it never come to us,

but ,if we don't pay much attention to it,and let it be,the thing we want will come to us naturally.

(3) question: how to express this meaning in an idiom?

Thank you in advance.

ps: I hope i make myself understood...:-)
A watched pot never boils. Good things come to those who wait.

Not quite your requested meaning though. I'm not sure we have one idiom that covers both ideas.
We have a nursery rhyme:

Little Bo-Peep
Has lost her sheep
And doesn't know where to find them.
Leave them alone
And they'll come home
Wagging their tails behind them.
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