Question

中译英《我已经在A公司工作2年了，在到A公司之前，我在B公司工作》。谢谢。

Answer 1

如果你现在仍在A公司工作，可以这样说：
I have been working at Company A for two years. Prior to that, I worked at Company B.

若你已经离开了A公司，应该这样说：
I worked at Company A for two years and at Company B before that.

Answer 2

I have been working at company A for two years. Before that/Prior to that, I worked at company B.