How do you say "we must say goodbye" in korean?

Hi my name is Kyungsik Sohn ( 손경식 ) The other answers are inaccurate or wrong or not enough
The Correct phrases are ::: #1 우리는 서로 작별 해야될때입니다
#2 우리는 서로 인사 해야될때입니다
#3 우리 서로 헤어져야 할 때입니다
#4 우리는 서로 이제 그만 가봐야 할때입니다
--------Pronunciations----------
1. Ouri nun soroe jackbyuel heya doil Ddae Eibneeda
2. Ouri nun soroe Insa heya doil Ddae Eibneeda
3. Ouri soroe haeyeujeuya hal Ddae Eibneeda
4. Ouri nun soroe eiijay geman gaboa hal Ddae Eibneeda

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These phrases are usually not used in reality. It's like the phrases you find in an act on stage.

What most Koreans usually use is
( if friends )1. 우리이제 각자 그냥 가자
2. 난 이만
3. 나 가볼게 안녕
--------Pronunciation--------
1. Ouri Ejay Kagja Geunyang gaja ( Let's just split up and go ( home, school ect ect it depends what you put on the back of the "가자" ) )
2. Nan Eman ( I'm leaving ( Bye ) )
3. Na gabolgay anyong ( I'm going to go now bye )

Hope I've helped !