Learn Hardcore Vietnamese: Bạn cần gửi gói hàng này trước cuối tháng. - You need to send this package before the end of the month.

Bạn is the second-person pronoun “you,” used to specify who is being addressed. Vietnamese often drops subject pronouns when context is obvious, so you could say
• Cần gửi gói hàng này trước cuối tháng.
—but including Bạn makes it clear and a bit more polite.

What part of speech is cần, and how does it function here?

Cần is a verb that means “need.” When followed by another verb (here gửi), it expresses necessity: “need to send.” It behaves like a modal auxiliary in English.

Why is there no word like “to” or “phải” between cần and gửi? When would you add phải?

In Vietnamese, cần can directly precede another verb without a particle. If you add phải—forming cần phải gửi—you simply emphasize the obligation even more, but it isn’t required for basic meaning.

Why does này come after gói hàng rather than before?

In Vietnamese the demonstrative follows the noun it modifies. So you say gói hàng này (“this package”) instead of này gói hàng.

Why isn’t there a classifier like cái before gói hàng? Could you add one?

Here gói hàng already includes gói (“package”) which doubles as a noun and a sort of classifier. You can add một or cái for emphasis or specificity:
• Bạn cần gửi một cái gói hàng này…
—but it isn’t necessary.

Is gói hàng the only way to say “package”? What about bưu kiện?

Gói hàng is the everyday term for “package.” Bưu kiện is more formal or used in postal contexts (“postal parcel”). Both are correct, but gửi bưu kiện sounds a bit more official.

What does trước cuối tháng literally mean? Could you rephrase it?

Literally trước cuối tháng = “before end (of) month.” It’s idiomatic for “before the end of the month.” You can also say:
• trước khi hết tháng (“before the month runs out”)
• trước cuối tháng này (“before the end of this month”) for extra clarity.

Can you move the time expression trước cuối tháng to the front?

Yes, Vietnamese allows fronting adverbials for emphasis or style:
• Trước cuối tháng, bạn cần gửi gói hàng này.
But the original order (Bạn cần gửi… trước cuối tháng) is more neutral and common.

How would you make this instruction more formal or polite?

You could replace Bạn with a title or omit it entirely, and use vui lòng to soften the tone:
• Vui lòng gửi gói hàng này trước cuối tháng.
• Quý khách vui lòng gửi bưu kiện trước khi hết tháng.