Learn Hardcore Chinese: Jīntiān wǒ děi xiān qù yínháng.

It’s a modal verb meaning must / have to. So 我得先去银行 means “I have to go to the bank first.” It expresses necessity, often based on the speaker’s judgment or circumstances, and sounds quite colloquial and natural in everyday speech.

I see the character 得. How do I pronounce it here, and how is it different from other “de/dei/de” sounds?

Here it’s děi (third tone), meaning “must.” The same character 得 can also be:

de (neutral tone) as a complement marker, e.g., 跑得快 (pǎo de kuài, “run fast”).
dé (second tone) meaning “to obtain,” e.g., 得到 (dédào, “to get”). Don’t confuse it with the particle 的 (de), which marks possession/attribution, or 地 (de), the adverbial particle.

Why is 先 placed before 去? Can it go anywhere else?

先 is an adverb meaning “first; before anything else,” and it typically goes before the main verb: 先去. Common options:

我得先去银行 (most common)
我先得去银行 (also fine; slightly different emphasis on “first”) Avoid 我去银行先 in standard Mandarin; that word order is regional/nonstandard.

How do I say “first do this, then do that” using 先?

Use the sequence pattern 先…，再… (or 然后):

我得先去银行，再去公司。 (Wǒ děi xiān qù yínháng, zài qù gōngsī.) “I have to go to the bank first, then go to the office.” You can also say 先…然后…最后… for longer sequences.

Why does the sentence start with 今天? Could I say 我今天… instead?

Time expressions like 今天 often come first as a topic: 今天，我得先去银行. It’s equally natural to say 我今天得先去银行. Both are correct; starting with 今天 foregrounds the time slightly more.

Are there any pronunciation or tone-sandhi issues in this sentence?

Yes:

我得 are two third tones in a row; the first becomes a rising tone in speech: wó děi.
银行 is pronounced yínháng (both second tone). The 行 here is háng, not xíng.

Why isn’t there a measure word or article before 银行? How do I say “a bank” or “the bank”?

With place/institution destinations, Chinese often uses bare nouns: 去银行 = “go to the bank (in general).” To say “a (specific) bank,” use a classifier:

去一家银行 (qù yì jiā yínháng) “go to a bank” For trips, you can add a “trip” classifier:
先去一趟银行 (xiān qù yí tàng yínháng) “first go to the bank (for a trip)” To specify “that (particular) bank”: 那家银行.

What’s the difference between 去 and 到 here? Could I say 到银行?

去 emphasizes the action of going: 去银行 “go to the bank.”
到 emphasizes arrival at the destination: 到银行 “arrive at the bank.” In many contexts both are fine: 我得先到/去银行. If you add another verb, use 去 + [do something]: 去银行办事/取钱.

Can I drop the subject 我?

Yes, Chinese allows subject drop if the subject is clear from context: 今天得先去银行 can still mean “(I) have to go to the bank first.” Use 我 when you need to avoid ambiguity.

Could I use 要, 必须, 需要, or 应该 instead of 得? What’s the nuance?

得 (děi): have to/must; colloquial, speaker’s judgment/necessity.
Example: 我得先去银行。
必须 (bìxū): must; stronger, more formal/absolute obligation.
我必须先去银行。
要 (yào): need to / be going to / want to (context-dependent, sometimes ambiguous).
我今天要先去银行。
需要 (xūyào): need (often more objective or “require”).
我需要先去银行。
应该 (yīnggāi): should/ought to (recommendation, weaker than must).
我应该先去银行。

Do I need 了 at the end? What would it change?

Sentence-final 了 can signal a new situation/decision or imminent action:

今天我得先去银行了。 “Looks like I have to go to the bank first (now/after all).” Without 了, it’s a neutral statement of necessity.

Is 先 necessary? What’s the meaning difference with and without it?

我得去银行: “I have to go to the bank” (no sequencing implied).
我得先去银行: “I have to go to the bank first (before doing other things).” So 先 explicitly marks priority/order.

How do I turn this into a question?

Two common ways:

Add 吗: 你今天得先去银行吗？ (Nǐ jīntiān děi xiān qù yínháng ma?) “Do you have to go to the bank first today?”
Use 是不是 for confirmation: 你今天是不是得先去银行？ Avoid an A-not-A form directly on 得; use 吗 or 是不是 instead, or put A-not-A on the main verb: 你今天先去不去银行？

How can I add the purpose, like “to withdraw money”?

Attach the purpose after the place:

我今天得先去银行取钱/存钱/换钱/办业务/办点事。 Or use 为了 to highlight purpose:
我今天得先去银行，为了开户。

Is 今天 the same as 今日?

Both mean “today,” but 今天 (jīntiān) is standard in everyday speech. 今日 (jīnrì) is more formal/literary and common in headlines, notices, or set phrases (e.g., on signs). In conversation, stick with 今天.