but u have 2 speak English什么意思？

但是你不得不说英语,它是我们都知道的

But you have to speak English,'cause it's all I know.
但你必须说英语,因为我只会英语

完全版应该是
But you have to speak English, because it's all i know.
就是说，但是你不得不说英语，因为那是我唯一懂的语言。

你那是缩写,应该是:
but you have to speak English, because it's all i know.

意思:你必须说英语,因为我只懂英语.

但你不得不说英语，因为我只听得懂英语.