“你在胡说八道”用英语怎么说？

You don't know what you are talking about.

【正确理解】你在胡说八道。

You don't begin to understand what they mean.

【正确理解】你根本不知道他们在干嘛。　(not begin to：毫不)

They didn't praise him slightly.

【正确理解】他们大大地表扬了他。