A2
在 before the verb — happening now
How Chinese marks an action in progress with 在 and 正在, why 呢 turns up at the end of these sentences, and why 我在住在北京 is wrong however natural “I’m living in Beijing” sounds.
在 in front of a verb says the action is going on right now. It is the same character as the 在 that marks location — Chinese treats being in the middle of doing something as a kind of place to be.
我在吃饭。
Wǒ zài chīfàn.
I’m eating.
他在看电视。
Tā zài kàn diànshì.
He’s watching television.
正在 for this exact moment
正 sharpens it to right now, as we speak. It is what you reach for when the timing is the point — someone rang and you are in the middle of something.
他正在开会。
Tā zhèngzài kāihuì.
He’s in a meeting right now.
我正在做饭，等一下。
Wǒ zhèngzài zuò fàn, děng yíxià.
I’m cooking, hang on.
呢 at the end
呢 softens the sentence and marks it as ongoing. It appears constantly with this pattern, often instead of 在 rather than alongside it, and it makes a question sound conversational rather than clipped.
你在做什么呢？
Nǐ zài zuò shénme ne?
What are you up to?
他睡觉呢。
Tā shuìjiào ne.
He’s asleep.
Not for states
This is the mistake English speakers make, and it is invisible from the English side because English uses its progressive for both. 在 marks an action under way. Living somewhere, knowing something, owning something and liking something are not actions.
我在住在北京。
我住在北京。
I’m living in Beijing is progressive in English and a plain statement in Chinese. The same goes for 我知道, 我有, 我喜欢 — none of them take 在.
The negative
没在, or 没有在. 不在 would be read as the location 在 — not at — which is a different sentence.
我没在看电视。
Wǒ méi zài kàn diànshì.
I wasn’t watching television.
Against 着
在 says the action is running. 着 says a state left behind by an action is holding. 他在开门 is he’s opening the door; 门开着 is the door is open. One is a film, the other a photograph.