英语翻译This a much larger question that what should happen with

英语翻译
This a much larger question that what should happen with undocumented workers,or how best to secure the border ,and it is one that affects not only newcomers but groups that have been for generations.
一,should 在这里是当作什么用的,happen with 是词组吗
二,and it is one that 这里 it指代什么 还有one指代什么 为什么这么用,
写错了开头是 This is