"get up to" in Chinese (Simplified)
干（某事，通常是不正当的事情）- 在做（某事）
Definition
指做某事，通常是偷偷摸摸或顽皮的事情。常用来问某人在忙什么，尤其当觉得他们做的事不寻常时。
Usage Notes (Chinese (Simplified))
属于英式英语的口语表达，常带有调皮或隐秘的含义。常用于询问他人在悄悄做什么，特别是小孩或朋友。美式英语更常说 'What are you up to?'。
Examples
What are you getting up to this weekend?
你这个周末**打算干什么**？
The kids must be getting up to something in the garden.
孩子们一定在花园里**干什么坏事**。
She always wants to know what I'm getting up to.
她总想知道我**在忙什么**。
I heard you and Tom were getting up to something last night!
听说你和汤姆昨晚**搞了些什么事**！
Who knows what the neighbors are getting up to behind closed doors?
谁知道邻居们关上门后**搞什么鬼呢**？
You never know what kids will get up to when they're bored.
小孩无聊的时候，谁知道他们会**干什么**。