这句话时态有错误吗?或者语法有错误吗?

问题描述:

这句话时态有错误吗?或者语法有错误吗?
We can see that when Willy found out that Biff stole the football,he didn’t criticize him,but praised his “Initiative spirit”.

把stole改写成had stolen
过去的过去要用过去完成时