Last night,after a supper,i went for a walk with 短文改错

Last night,after a supper,i went for a walk with 短文改错
Last night,after a supper,i went for a walk with
some of my classmates.We happen to see some
foreign friends take a walk,too.I said "Good night"
to them and they answered"Good wvening"with
a smile.I was wondering on my way back to home.
Why do they say "Good evening"instead"Good
night"when they meet people at the night?Iwent to
the teacher for helping.Then I understood I made a
mistake with everyday English.Now I know it is very
important of us to use everyday English correctly.