one, two, etc. down, one, two etc. to go. idiom
已经完成了一／两个，还有一／两个没完成呢
an expression that is used to mean that you have done or dealt with the first, second, etc. of a series of things and have yet to do or deal with the rest
"How are your finals going?" "Two down, three to go." “你的期末考试考完了吗？”“考完两个了，还剩三个没考呢。”