I can pretty much understand what you are talking about.

我非常能了解你在说些什么。

pretty 在这里完全等于 very 的意思，但是你在这里就不能用 very 来代替 pretty。或是你可以把 pretty 改成 pretty much，就成了 I can pretty much understand what you are talking about. 这种用法在日常生活中十分常见，例如他们会说 We are pretty much the same, 就是我们非常相像的意思。