Learn Hardcore Chinese: tā xiàbān yǐhòu zài gōngyuán pǎobù.

You can sometimes see 在下班以后 in writing or formal speech, but it sounds more like “during the period after work” and is not needed here. For normal spoken Mandarin, simply use 下班以后 without 在.

Why do we say 在公园跑步 and not just 公园跑步?

在 (zài) is used to introduce a location where an action happens.

Basic pattern:

在 + place + verb / action

So:

在公园跑步 – run in the park
在家看电视 – watch TV at home
在学校学习 – study at school

If you only say 公园跑步, it sounds incomplete or poetic at best. In standard speech, you almost always put 在 before the place phrase when it’s modifying a verb like this.

What is the difference between 跑 and 跑步? Can I say 他下班以后在公园跑?

Both are related to running, but they’re used a bit differently:

跑 (pǎo) – to run (general verb)
步 (bù) – step
跑步 (pǎobù) – literally “run steps”; used as a set verb meaning “to run / to jog (as exercise)”

In this context (exercise), 跑步 is more natural:

他下班以后在公园跑步。 ✅
He runs/jogs in the park after work.

You can hear:

他下班以后在公园跑。

This is understandable, but it can feel slightly less like “go jogging” and more like “runs (around / runs off)” depending on context. For talking about exercise / jogging, 跑步 is the standard choice.

Is this sentence talking about a habit (he usually does this) or one specific time?

Chinese verbs do not change form for tense like English does. Whether it’s habitual or one-time depends on context and extra words.

Your sentence by itself most naturally suggests a habitual action:

他下班以后在公园跑步。
→ He runs in the park after work. (regular habit)

To make it clearly habitual, you can add adverbs:

他每天下班以后在公园跑步。
He runs in the park after work every day.
他常常下班以后在公园跑步。
He often runs in the park after work.

To make it more clearly one specific future time, you can say:

他下班以后会在公园跑步。
He will run in the park after work.
Or add a specific time: 今天下班以后… – after work today…

So context and extra words decide the nuance.

If I want to say clearly “He will run in the park after work”, what should I add?

You can add 会 (huì) to show a likely or planned future action:

他下班以后会在公园跑步。
He will run in the park after work.

Or you can specify the time:

今天下班以后他在公园跑步。
After work today, he will run in the park.
(Here 今天 and 下班以后 make it clear we’re talking about the future.)

Often, just context (like talking about tonight’s plan) is enough, but 会 is the most common explicit marker for future in a sentence like this.

Why is there no 了 in this sentence? Could I say 他下班以后在公园跑步了?

了 (le) often marks completion or change of state.

Your original sentence without 了 is neutral and usually sounds habitual:

他下班以后在公园跑步。
He runs in the park after work. (a routine)

Adding 了:

他下班以后在公园跑步了。

This sounds like you’re talking about a completed event in a particular time frame, or a new situation that has started. For example, in a story context:

昨天他下班以后在公园跑步了。
Yesterday, after work, he ran in the park. (specific instance)

So:

For habits → usually no 了.
For specific finished events (especially with a time word like 昨天) → 了 is common.

Can I change the word order to 他在公园下班以后跑步?

No, that word order is not natural and is confusing.

Standard pattern for time and place is:

Time → 2. Place → 3. Action

Your sentence follows that:

下班以后 – after work (time)
在公园 – in the park (place)
跑步 – run (action)

So:

他下班以后在公园跑步。 ✅

If you say 他在公园下班以后跑步, it sounds like:

“He, in the park, after getting off work, runs” – but “get off work in the park” is strange; work is normally at a company, not in a park.

So keep 下班以后 together as a time phrase near the beginning, then 在公园, then 跑步.

Could I say 他下班以后在公园里跑步? What is the difference between 在公园 and 在公园里?

Yes, you can:

他下班以后在公园里跑步。 ✅

Difference:

在公园 – in the park (neutral)
在公园里 – literally “inside the park”; sometimes sounds a bit more specific or slightly more vivid, emphasizing the inside of the park.

In many contexts, 在公园 and 在公园里 are interchangeable, and both are natural. The 里 (lǐ) is optional here.

How would I say the negative: “He doesn’t run in the park after work”?

You can negate it with 不 (bù):

Simple negation of the action:

他下班以后不在公园跑步。
He doesn’t run in the park after work.

If you want to emphasize that he doesn’t go there to run, you can say:

他下班以后不去公园跑步。
After work he doesn’t go to the park to run.

Both are correct; the second one highlights going to the park as well as running.

What exactly does 他 (tā) refer to? In English, “he” and “she” are different.

Spoken Mandarin does not distinguish gender in pronunciation for he / she / it:

他 (tā) – he (written with the “person” radical)
她 (tā) – she (written with the “woman” radical)
它 (tā) – it (for things, animals, etc.)

All are pronounced tā.

In your sentence:

他下班以后在公园跑步。

From speech alone, it could be he or she.
Only the written character 他 tells you it’s “he”. In a spoken conversation, you know from context whether the person is male or female.