谁能帮我分析下这个句子是个什么从句，句子结构是什么？

Question

there were a few points in the essay he had founded impossible to understand.

Answer 1

there were a few points in the essay he had founded impossible to understand.
he had founded impossible to understand是一个定语从句修饰a few points
主句是there were a few points 状语是in the essay
在那个散文里，有一些他觉得难以理解的地方。追问

你能帮我看看这个句子吗，这个专四真题，它说从句要用过去完成时，为什么there were不用过去完成时呢？只有founded需要用过去完成时？？？

Answer 2

是定语从句，essay后面的是定语，用来修饰essay。essay后面省略了that