My boyfriend is Brazilian and he's wondering whether you would say "He's in the sidewalk" or "He's on the sidewalk" "on the sidewalk" sounds right to me.
But when you're talking about a street, the house would be ON the street but the kids would be playing IN the street. The way he sees it is the kids are IN the street because the street is an enclosed area. The house is ON the street because that's where the house is located but it's not actually on the physical street, but to the side of the street.
So he feels like the sidewalk is an enclosed area, therefore we should say that someone is in the sidewalk and not on the sidewalk.
So would the correct answer be "He was walking in the sidewalk" or "He was walking on the sidewalk"
In American English, we walk "on" the sidewalk.
Walking "in" the sidewalk sounds like the cement has just been poured and you're ankle-deep in it.
Note that "on the street" and "in the street" are different, depending on whether you are in the US or the UK.