Hi, I'm trying to identify this movie I am pretty sure was Korean.

All I can remember are specific scenes of the movie, hopefully they trigger somebody's memory if they know it.
It was made in either the 80s or 90s I think.
The main storyline seems to be about a girl who is struggling with the city life.
An opening scene has someone being chased on a motorbike by some government secret organisation through the city. The biker being chased crashes by a lake, ut is not found.
The main girl has a pretty lousy sister who doesn't really help much.
The main girl has a black friend, who does boxing and is supposed to fight very soon. He gets ill or injured and cannot fight. She steps in, and fights this huge man. She wins if I remember right.
There is also a scene with the lazy sister having an arm wrestling match with some massive guy, and she wins too, via illegal tactics.
Not sure if this will trigger anyone's memory, thanks anyway.