don't you say "watchman" for guardian in english ? Here in Peru ( also in Ecuador but less) they call the guardian " wachiman). when I settled here 26 years ago, I had no idea what a " wachiman" could mean in spanish !! ( i mean in spanglish )worse so because my mother tongue is French. !!) in French guardian is gardien.
Ah ha. "Guard" or "security guard" is the correct English translation. "Watchman" also should be accepted.
In English a "guardian" is the person who acts as a child's parent when the birth parents are dead, missing, or absent. For example, "If my parents die, then my aunt will become my guardian."