The first class is English.

第一节是英语课。

The first class is Chinese.

第一节课是语文。

This is my Chinese teacher told me in the first class.

这是我的语文老师在第一节课的时候说的。

Running towards the school, I took a glance at my watch and found that I was already late for the first class.

我一边朝学校跑去，一边看一眼手表，发现我第一节课已经迟到了。

He sat quietly in the first class cabin of the flight looking tired.

他静静地坐在班机的头等舱内，看上去有些疲惫。