You use upper to describe something that is above something else.
There is a good restaurant on the upper floor.
楼上有一家很好的餐馆。
his upper lip.
他的上嘴唇。
Students travel on the cheap lower deck and tourists on the upper.
学生们坐廉价的下层舱,游客们坐上层舱。
You use upper to describe the higher part of something.
the upper part of the foot.
脚面。
the muscles of the upper back and chest.
上背部和胸部的肌肉。
the upper hand
If you have the upper hand in a situation, you have an advantage over other people involved, for example because you have more power or success.
The home team was beginning to gain the upper hand.
主队正开始占上风。