"Five fifty" in Engpsh is a way of referring to the time 5:50.
It is commonly used in everyday language and is derived from the way people typically express time on a 12-hour clock, by combining the number of hours with the number of minutes.
Examples:
"I'll meet you at five fifty."
"The movie starts at five fifty."
Translations:
"我们五点五十见面。"
"电影五点五十开始。"