In Japan, there was any high school teacher to tell us the phrase “Oh boy!”.

I heard this phrase when I bought a TV and brought it to home by myself.
When the elevator’s door opened and the woman came out from it, then she said “Oh boy!”.

I didn’t understand what that means.
Boy? Do I look so young? But I’m over 30 years old. Not Boy.

Finally, I found that phrase when I studied English at online course.
I have been studying English over 15 years, but anyone didn’t tell that phrase.

I think that to study the phrases to use “real” conversation is important in Japan.
When Japanese begin to study English in junior high school, they learned a strange sentence. Do you know it? That is,

“Is this a pen?” - “No, it is a desk.”