Learn Hardcore Indonesian: Proposal yang kamu kirim minggu lalu sudah disetujui oleh fakultas. - The proposal that you sent last week has already been approved by the faculty.

So yang works like English that/which/who in relative clauses.
Without yang, kamu kirim would not clearly attach to proposal in a standard, careful sentence.

Why is it "kamu kirim" and not "kamu mengirim" or "kamu mengirimkan"?

In Indonesian, after yang, it’s very common to use the base verb (without the me- prefix), especially in spoken or neutral style:

yang kamu kirim = that you sent
yang kamu mengirim – sounds wrong
yang kamu mengirimkan – grammatical but feels heavier / more formal

You could say:

Proposal yang kamu kirimkan minggu lalu...

This is also correct and a bit more formal or complete. But yang kamu kirim is perfectly natural and common.

Is "yang kamu kirim" active or passive? How does it work?

Yang kamu kirim is active voice:

kamu = subject (you)
kirim = base verb send
(object = proposal, placed before as the head noun)

The structure is:

[Noun] + yang + [subject] + [verb]
Proposal yang kamu kirim = the proposal that you sent

So the “sending” is done by you (active), not to you.

Can I say "Proposal kamu kirim minggu lalu..." without yang?

In everyday spoken Indonesian, you might hear Proposal kamu kirim minggu lalu..., but it sounds a bit informal and slightly unpolished.

In neutral or careful Indonesian, it’s better to include yang:

Proposal yang kamu kirim minggu lalu...

So:

With yang = clearly correct and natural in speech and writing
Without yang = can appear in casual speech, but is not the standard pattern you should learn first

Where can "minggu lalu" go in the sentence? Is its position fixed?

Its position is fairly flexible, as long as it’s clear what it modifies. All of these are natural:

Proposal yang kamu kirim minggu lalu sudah disetujui oleh fakultas.
Proposal yang minggu lalu kamu kirim sudah disetujui oleh fakultas. (more emphasis on last week)
Minggu lalu, proposal yang kamu kirim sudah disetujui oleh fakultas. (topic fronting: as for last week...)

What you wouldn’t normally say is splitting it oddly, like:

✗ Proposal minggu lalu yang kamu kirim (this sounds like “the last-week proposal that you sent,” which is odd)

Default, neutral choice: keep minggu lalu close to kamu kirim.

What’s the function of sudah in this sentence?

Sudah indicates that the action is already completed:

sudah disetujui = has already been approved / was approved

If you remove sudah:

Proposal yang kamu kirim minggu lalu disetujui oleh fakultas.

This is still grammatical, but it sounds more like a simple fact (approved at some point), without emphasizing that it’s already done (e.g., in contrast to expectations, or to something pending).

What does disetujui mean grammatically? Why is there di-?

Disetujui is the passive form of the verb setuju (agree/approve):

setuju = to agree
menyetujui = to approve (active; someone approves something)
disetujui = to be approved (passive; something is approved by someone)

In this sentence:

Proposal ... sudah disetujui (oleh fakultas).
= The proposal has been approved (by the faculty).

The di- prefix marks passive voice. The -i is a common verb suffix forming menyetujui / disetujui from setuju.

Is oleh necessary in "oleh fakultas"? Can I drop it?

You can safely drop oleh here:

Proposal ... sudah disetujui oleh fakultas.
Proposal ... sudah disetujui fakultas.

Both are grammatical. Differences:

oleh fakultas – a bit more explicit and formal, clearly marking the agent.
fakultas (without oleh) – more compact, common in speech and informal writing.

In many passive sentences, oleh is optional if the agent is clear and short.

What exactly does fakultas mean here? Is it like “the faculty members” or “the department”?

Fakultas in Indonesian usually refers to an academic faculty as a unit of an institution (e.g., Faculty of Engineering, Faculty of Law), not the individual professors.

In this sentence, fakultas most naturally means:

the Faculty (as an administrative body) has approved it

If you want to emphasize the people or office, you can also say:

pihak fakultas = the faculty side / the faculty (as an institution)
dekanat = the dean’s office (if that’s what you specifically mean)

Should it be "fakultasnya" to mean “the faculty”?

You don’t need -nya here. In Indonesian:

fakultas = the faculty (when context is clear; no article needed)
fakultasnya = the faculty with a nuance of “that faculty / its faculty / their faculty” depending on context

So:

... disetujui oleh fakultas. – normal, generic “the faculty” in this context
... disetujui oleh fakultasnya. – could imply “by its faculty / by that particular faculty we’ve been talking about”

In most cases like this, plain fakultas is preferred.

How formal is kamu? Would Anda be better?

Kamu is informal / neutral, used:

with friends
with people your age or younger
in casual settings

Anda is polite and formal, used:

in customer-facing contexts
in official letters or announcements
when speaking respectfully to someone you don’t know well

So you might also say:

Proposal yang Anda kirim minggu lalu sudah disetujui oleh fakultas.

This sounds more polite and is suitable in a formal email to a student or colleague.

Why don’t we use "telah" instead of "sudah"? Are they the same?

Sudah and telah both mark a completed action, but their tone is different:

sudah – neutral; common in both speech and writing
telah – more formal / literary / official

You could say:

Proposal yang kamu kirim minggu lalu telah disetujui oleh fakultas.

This is perfectly correct and sounds more formal, like an official announcement or letter. In everyday conversation, sudah is more natural.

How do I pronounce disetujui? It looks tricky.

Break it into syllables:

di-se-tu-ju-i

Approximate pronunciation:

di – like dee
se – like suh
tu – like too
ju – like joo
i – like ee

So it flows as: dee-suh-TOO-joo-ee (stress is usually slightly heavier on tu: se-TU).