Go pee-pee 去小便；尿尿
Do you need to go pee-pee?
你要去尿尿吗？
The child will tell their parents they need to "go pee-pee."
小孩子需要尿尿的时候会告诉他们的父母。

Take a leak 撒尿
Yes! I need to go take a leak.
是的！我要去方便一下（撒泡尿）。

Going to the ladies'/men's room 去男/女洗手间（厕所）
Men will say they are going to the men's room when guys are being polite.
出于礼貌，男生会说他们要去男洗手间。
Have you heard some say they are going to the ladies' room?
你听到过有人说“我要去女洗手间”吗？

Fix my makeup 补个妆
So, you would just say to your date, "Oh, I need to go fix my makeup."
所以你会直接跟你的约会对象说：“哦，我得去补个妆。”

I gotta go 我要走了；我得走了
Your friend will ask, "what's wrong?" and you could just say, "I gotta go."
你的朋友会问“怎么了? ”你可以直接说“我得走了”。

I'll be right back 我马上回来
Guys, I'll be right back.
哥几个，我马上回来。