My English teacher speaks too fast.We can know what she is talking about.

My English teacher speaks too fast. We can't know what she is talking about.
=My English teacher speaks so fast that we can't know what she is talking about.

My English teacher speaks too fast. We can know what she is talking about.
我的英语老师说话太快. 我们也听懂她在谈论什么 .
你这句话像话吗？
前面的那句是要表达＂太快＂，　那后一句话因该是要写＂太快＂的副作用，　那后局因该有反义的意思．
我的英文老师说得太快了，　所以我们都没听明白。　
My English teacher speaks too fast so we cannot understand what is she talking about.

我的英语老师说话太快，我们也听懂她在谈论什么

My English teacher speaks too fast. We can know what she is talking about.
My English teacher speaks too fast. We can't know what she is talking about.
应该要表达的是下面这个意思吧

你的问题是什么?

这句话的意思是：我的英语老师说话太快，我们听不懂她在谈论什么。