Smile

My face is now cross because I am not happy with retaking exams and preparation for it. When I was on the train today on my way home, my face was cross face.
One men knocked the window from outside. I was wondering what he wanted. He wanted to make me open the door or something??
No!! what he meant was not that. Something else. He pointed his mouth and said something.
I did not understand him immediately and stared him.
He said “Smile” and he made smile pointing his mouth.
After the train left the station, I made smile on my own.