to begin with idiom
B1 原先，刚开始时
at the start of a process, event, or situation
There were six of us to begin with, then two people left. 原先，我们有6个人，后来走了两个。
B2 首先，第一
used to give the first important reason for something
The hotel was awful! To begin with, our room was far too small. 这家旅馆太差了！首先是我们的房间太小。