YOU SAID:

i was walking down the sidewalk and saw a girl smiling at me

INTO JAPANESE

私は歩道を歩いていて、女の子が私に微笑んでいるのを見ました

BACK INTO ENGLISH

I was walking on the sidewalk and saw a girl smiling at me

INTO JAPANESE

私は歩道を歩いていて、女の子が私に微笑んでいるのを見ました

BACK INTO ENGLISH

I was walking on the sidewalk and saw a girl smiling at me