When I arrived in China. The first time I got to China.

"第一次来中国"用英语是"First time coming to China." “第一次做某是“用英语应该是"First time doing something." 不是 "First time do something." 没有美国人说第三个英语句子.

When I first arrived in China/ When I first got to China. **implies that you are no longer in China. When I first came to China/ When I first got to China. **implies that you are still in China. **"to get" is a more informal word and covers more grounds. Generally if the action is taking place in the present, it would be "first time doing smthg" because "to do" is the infinitive form, indicating that there is a time setter before it, like "it *will* be the first time to do smthg". Hope this helps! :)