我对这部分不太清楚?用英文怎么说呢?

1:I am part of it is not very clear.
2:I understand that not very to this part.
3:The subject is unfamiliar to me.

以上说法都可以，相信我，我读的大学就是外语学院。

I am not too clear to this part?

I'm not so sure about this

I don't know this part exactly.