你真能干英语可以翻译为"You're really good at English." 这句话的来源可能是由于在中文里，"干"这个词常常被用来形容一个人很擅长或很有能力做某事。

例句:

你真能干英语，讲得真好。(You're really good at English, you speak it well.)

他真能干，每次考试都能得满分。(He's really talented, he gets full marks on every exam.)

她真能干，从来不拖延工作。(She's really efficient, she never procrastinates on her work.)