Learn Hardcore Chinese: Wǒmen xiàge xīngqī yǒu zhōngwén kǎoshì, wǒ děi hǎohāo zhǔnbèi. - We have a Chinese exam next week; I have to prepare well.

Using 是 would sound like you are defining what “next week” is, almost like:
下个星期是中文考试 → “Next week is Chinese exam,” which is not natural as a way to say “we have an exam next week.”

So for events that will happen (classes, meetings, exams, activities), Chinese typically uses 有:

明天有会议。= There is a meeting tomorrow / We have a meeting tomorrow.
星期五有中文课。= We have Chinese class on Friday.

What is the function of 得 (děi) here, and how is it different from other 得 that I’ve seen?

In this sentence, 得 (děi) is a modal verb meaning “must / have to / need to”:

我得好好准备。
= I must prepare well.

This 得 is pronounced děi (third tone) and always comes before a verb phrase.

There is another very common 得 (de) (neutral tone) that acts as a particle after verbs or adjectives, introducing a complement:

说得很快 = to speak (in such a way that it is) very fast
他跑得很慢 = he runs (in such a way that it is) very slowly

So:

得 (děi) = must / have to
得 (de) = structural particle after a verb or adjective

In your sentence, it is clearly the “must” one: 我得准备.

How is 得 (děi) “must” different from 要, 需要, and 必须?

All of these can express some kind of necessity, but the tone and usage differ:

得 (děi)
- Everyday spoken Chinese, fairly informal.
- Often implies personal feeling or practical necessity.
- 我得走了。= I gotta go.
要 (yào)
- Can mean want to, will, or have to, depending on context.
- As “have to,” it’s similar to 得, sometimes a bit more matter‑of‑fact.
- 我明天要考试。= I have an exam tomorrow.
- 我得好好准备 / 我要好好准备 = I have to prepare well (very similar here).
需要 (xūyào)
- More like “need” than “must.”
- Often used for objective needs.
- 我需要多练习中文。= I need to practice Chinese more.
必须 (bìxū)
- Strong, formal “must / absolutely have to”.
- Often used in rules, instructions, or strong insistence.
- 你必须按时交作业。= You must hand in your homework on time.

In your sentence, 我得好好准备 sounds natural and conversational, like “I really have to study properly.”

Why is it 下个星期 and not just 下星期 or 下周? Are there differences?

All of these are understandable and correct, but they differ slightly in style/region:

下个星期
- Very common in Mainland Mandarin.
- Literally “the next one week” (个 is a measure word).
下星期
- Also common, and often heard in southern China and in Hong Kong / Cantonese‑influenced areas.
- Slightly shorter; dropping 个 is natural in speech.
下周
- Uses 周 instead of 星期.
- Sounds a bit more concise / formal, common in news, work, or written language.

In everyday spoken Mandarin in the mainland, both 下个星期 and 下星期 are fine; 下个星期 might feel just a bit more standard‑textbook.

Why do we put 下个星期 between 我们 and 有? Can it go somewhere else?

Chinese time expressions are flexible in position, but there are common preferred spots. In your sentence:

我们 / 下个星期 / 有 / 中文考试

This is Subject – Time – Verb – Object, which is very natural.

You could also say:

下个星期我们有中文考试。
我们有中文考试，下个星期。 (last one is more like adding the time as an afterthought)

Typical positions for time words are:

At the beginning of the sentence:
- 下个星期，我们有中文考试。
Right before the verb (after the subject):
- 我们下个星期有中文考试。

Both (1) and (2) are extremely common and correct. The version you have is one of the most typical patterns learners should copy.

Why is there a 个 in 下个星期? Can I always put 个 before 星期?

个 here is a measure word (classifier). 星期 behaves like a counted unit of time, so you can think of:

一个星期 = one week
下个星期 = the next (one) week

Dropping 个 is common in some phrases:

下个星期 / 下星期
上个星期 / 上星期

So:

下个星期 and 下星期 are both correct.
In other contexts, you still need 个, for example:
- 我等了一个星期。= I waited for a week. (you can’t drop 个 here)

What exactly does 好好 mean here, and why isn’t it 好好地准备?

好好 in 好好准备 means “properly / carefully / really well”.

Grammatically, it’s an adverbial form derived from the adjective 好 (good). In formal grammar you might expect 好好地准备 (adverb + 地 + verb), but in everyday speech:

好好 + verb is extremely common, especially with monosyllabic verbs like:
- 好好学
- 好好想想
- 好好休息
- 好好准备

好好地准备 is also correct, but 好好准备 sounds more natural and colloquial. The 地 is often dropped when the adverb is short and fixed.

So:
我得好好准备。 = I have to prepare properly / really put effort into preparing.

Why is it 中文考试 and not 汉语考试? Is there a difference between 中文 and 汉语?

Both can appear before 考试, but their nuance is slightly different:

汉语
- Specifically the Chinese (spoken) language of the Han people.
- Often used in language‑learning contexts: 汉语课, 学汉语.
中文
- Broader: the Chinese language in general, including spoken and written, or anything “in Chinese.”
- Common in school or everyday speech: 中文课, 中文老师, 中文水平.

For a school exam, 中文考试 is very natural; it can imply an exam covering reading, writing, maybe grammar, etc. 汉语考试 is also possible, especially if you emphasise it as a foreign language test.

How does Chinese show that this is about the future (next week) even though there’s no word like “will”?

Chinese does not have verb tense in the same way English does. Instead, it relies on:

Time expressions: 下个星期, 明天, 以后
Sometimes aspect markers or modal verbs.

Here, the future meaning comes from 下个星期 alone:

我们下个星期有中文考试。
Literally: We next week have Chinese exam.
Interpreted as: We will have a Chinese exam next week.

You could add 会 to emphasise futurity, but it’s not necessary:

我们下个星期会有中文考试。 (still okay)

Normally, if the time word clearly indicates the future, native speakers omit 会.

Why is there a comma between the two parts of the sentence, and how does that compare to English punctuation?

The original is:

我们下个星期有中文考试，我得好好准备。

In Chinese, a comma (，) can link two closely related clauses, where in English you might use:

a semicolon:
“We have a Chinese exam next week; I must prepare well.”
or a full stop:
“We have a Chinese exam next week. I must prepare well.”

Chinese writes long sentences more freely with commas between clauses. The relationship here is cause/result:

Because we have an exam next week → I must prepare well.

In English, you wouldn’t join the two with just a comma (that would be a comma splice), but in Chinese that’s totally normal.

Could I drop 我们 and just say 下个星期有中文考试?

Yes, you can. It would mean roughly:

下个星期有中文考试。
= There is a Chinese test next week.

Chinese often drops subjects when they’re obvious from context. Whether you say:

我们下个星期有中文考试 (We have…)
下个星期有中文考试 (There is… / There will be…)

depends on what you want to emphasize:

If you’re talking specifically about your class / your group, using 我们 makes that clear.
If you’re just announcing the event, without focusing on who it’s for, you might omit 我们.

Does 准备 mean “prepare” in general, or does it specifically mean “study” here? Could I use 复习 instead?

准备 (zhǔnbèi) means to prepare in a broad sense:

准备晚饭 = prepare dinner
准备行李 = prepare luggage
准备考试 = prepare for an exam

In your sentence:

我得好好准备。
Context makes it clear: “I must prepare for the exam,” so it implies studying, reviewing materials, etc.

复习 (fùxí) specifically means to review (what you have learned), like going over your notes:

我得好好复习。= I have to review properly.

You could say:

下个星期有中文考试，我得好好复习。
= We have a Chinese exam next week; I really need to review properly.

That emphasizes going over learned content, whereas 准备 is more general “get ready,” which is the more flexible, default choice.

Is there any difference in meaning or tone if I say 我要好好准备 instead of 我得好好准备?

Both are very natural and often interchangeable in this context:

我得好好准备。
- Feels like: “I’ve got to / I must prepare well.”
- Slightly stronger sense of obligation or necessity.
我要好好准备。
- Can mean “I’m going to prepare well” or “I want to prepare well,” depending on context and intonation.
- Often sounds a bit more determined / volitional: “I’m going to (make sure I) prepare well.”

In daily conversation about an upcoming exam, either one is fine.
Subtle nuance:

得: more about necessity.
要: mixes necessity with intention: “I will / I’m going to.”