"你好笨" 用英语可以说 "You're so dumb"。
这个短语来自英语中的 "dumb"，它的意思是"无言的，哑的"，也有"愚蠢的，笨的"的意思。
例句:
"You're so dumb. How could you not know that?" (你太笨了，怎么会不知道?)
"He is such a dumb person, he can't even tie his own shoelaces." (他太笨了，连鞋带都系不好)
"I can't bepeve you fell for that dumb prank." (真不敢相信你会上当那个愚蠢的恶作剧)