Question

quando eu uso while e quando eu uso when ???

Answer 1

While = enquanto
When = quando 
"WHILE I was waiting for him" = "ENQUANTO eu estava esperando por ele"
"When I was at my room, my mother called me" "QUANDO eu estava no meu quarto, minha mãe me ligou"

Answer 2

When usa para um momento específico e não contínuo
Ex:When I was playing videogame,it started to rain

While usa para um evento simultâneo
Ex: While I was sleeping ,there was an explosion