I'm curious about elevator and sidewalk etiquette in South Korea.

Since moving to Korea, I've been confused about the etiquette in elevators and on sidewalks. Often, when I try to get off the elevator, someone is trying to come in right away. Especially today, I saw a child standing at the door of an officetel in Gangnam, holding their parent's hand and blocking the way. I'm curious if this is normal in a country with a high population density like Korea. While people in the subway line up well and let those getting off go first, why does this happen so often in elevators? I also experience similar confusion on the sidewalks. Since cars drive on the right in Korea, I thought it would make sense to walk on the right as well, but people often walk towards me. When I'm walking in Hongdae and my path crosses with someone else's, is it correct to step aside for each other? Or is this a kind of cultural norm? This situation continues to be a bit bewildering. If anyone has advice or experiences regarding this phenomenon, I would appreciate it if you could share.