first不是连词，是序数词
例句
1、
Take the first right， then the second left.
在第一个路口向右拐，然后再在第二个路口向左拐。
2、
His first music teacher was a major influence in his life.
他的第一位音乐老师是他一生中对他影响非常大的人。
3、
Mark has two children to support from his first marriage.
马克得扶养他第一次婚姻生的两个孩子。