Learn Hardcore Chinese: Tā zài gōngyuán ménkǒu hē kāfēi. - He is drinking coffee at the park entrance.

Location use: 他在公园门口喝咖啡 (Tā zài gōngyuán ménkǒu hē kāfēi).
Progressive use (no place specified): 他在喝咖啡 or, if you want both location and ongoingness, use 正在: 他正在公园门口喝咖啡. Avoid doubling 在 (e.g., 他在公园门口在喝咖啡) in standard speech.

Can I put the place at the end, like “他喝咖啡在公园门口”?

That word order is uncommon/marked. In Chinese, adverbials such as place normally go before the verb:

Natural: 他在公园门口喝咖啡.
End-position place is only used in special emphatic styles; avoid it as a learner.

Do I need 在 before 公园门口, or can I say “他公园门口喝咖啡”?

You generally need 在 to introduce the location adverbial. 他在公园门口喝咖啡 is standard. Omitting 在 makes it sound like a noun pile and is not normal in this structure.

What’s the difference between 门, 门口, 大门, 入口, and 门外?

门: door/gate (the object or concept).
门口: the doorway/entrance area (around the threshold, not strictly inside or outside).
大门: the main gate/primary entrance.
入口: the entry point (often on signs/maps; formal).
门外/门里: outside/inside the gate. Examples:
在公园门口 = at the entrance area.
在公园入口 = at the entry point (more formal).
在公园门外 = outside the gate.

Is 在公园门口 the same as 在公园的门口?

Both are correct. With location nouns like 门口/旁边/里面/外面, Chinese often drops 的:

在公园门口 (more natural in speech)
在公园的门口 (a bit more explicit/formal)

How do I express past or completed action here?

Use time words and/or 了:

Completed action: 他在公园门口喝了咖啡; even more natural with a measure: 他在公园门口喝了一杯咖啡.
Past time word: 他昨天在公园门口喝咖啡 (past is clear from 昨天).

How do I negate this sentence?

Habit/general statement: 他不在公园门口喝咖啡 (“He doesn’t (generally) drink coffee at the park entrance.”)
Specific/ongoing event: 他没(有)在公园门口喝咖啡 (“He wasn’t/isn’t drinking coffee at the park entrance.”) To say “right now he isn’t there doing it”: 他现在没在公园门口喝咖啡.

How do I say “a cup/two cups of coffee” in this sentence?

Use the measure word 杯 (bēi):

一杯咖啡, 两杯咖啡. Examples:
Completed: 他在公园门口喝了两杯咖啡.
Ongoing with emphasis: 他正在公园门口喝一杯咖啡.

Where do time words go relative to place?

Typical order: Subject + Time + Place + Verb + Object.

他今天在公园门口喝咖啡.
他明天会在公园门口喝咖啡.

How do I read this? What are the tones?

Tā zài gōngyuán ménkǒu hē kāfēi.

他 tā (1), 在 zài (4), 公园 gōngyuán (1,2), 门口 ménkǒu (2,3), 喝 hē (1), 咖啡 kāfēi (1,1). Note: 他/她/它 are all pronounced tā.

Can I use 到 instead of 在?

到 emphasizes movement toward a destination/purpose: 他到公园门口喝咖啡 = “He goes to the park entrance to drink coffee.”
在 describes location during the action: 他在公园门口喝咖啡 = “He drinks coffee at the park entrance.” Choose based on whether you’re emphasizing going-to or being-at.

How do I make this a yes–no question?

Add 吗: 他在公园门口喝咖啡吗？
A-not-A:
- On location: 他在不在公园门口喝咖啡？
- On the verb: 他在公园门口喝不喝咖啡？

Can I drop the subject if it’s obvious?

Yes. Chinese allows subject omission when context makes it clear:

在公园门口喝咖啡。 (…is [someone] drinking coffee at the park entrance.) In a full, standalone sentence, keep the subject: 他在公园门口喝咖啡。

Does 门口 specify inside or outside the gate?

No. 门口 means the entrance area (near the threshold) without specifying side. If needed:

Outside: 在公园门外.
Inside: 在公园门里 or 在公园里靠近门口.

Can I front the object for emphasis?

Yes, via topicalization:

咖啡，他在公园门口喝。 This emphasizes “coffee.” It’s colloquial/emphatic; the neutral order is still 他在公园门口喝咖啡.

Why is there no “the/a” like in English?

Chinese doesn’t use articles. Definiteness comes from context or modifiers. 公园门口 can mean “the park entrance” if the park is understood. To be explicit, add a modifier: 这个公园的门口 (“the entrance of this park”).