我刚学完英语回来是不是 I have came back just learn English`~?

i have just come back from a english class.
i'm just joking.

不是...语法不对

I was learning English before I came back.
我回来之前在学英语，意思差不多吧...

开玩笑
Just kidding.

开玩笑 joke kid
你开玩笑呢吧？are you joking?are you kiding me?

I just come back from my English learning`~?

I have just learned English.
开玩笑：make a jok

在聊天的时候可以直接告诉对方，just kidding 这是在开玩笑的。
开玩笑，我见过另外的翻译的是play jokes