Learn Hardcore Indonesian: Saya selesai mengerjakan PR tadi malam, walaupun seringkali saya mengantuk setelah kerja. - I finished doing the homework last night, although I am often sleepy after work.

Saya mengerjakan PR tadi malam means I did my homework last night and doesn’t clearly say that you finished it.
The pattern saya selesai mengerjakan PR literally means I am finished doing the homework, which implies the task is completed.

Other common ways to say I finished my homework are:

Saya sudah menyelesaikan PR saya.
Saya sudah selesai dengan PR saya.

So selesai mengerjakan PR emphasizes completion, not just doing it.

What exactly does PR mean in Indonesian, and is it informal?

PR is an abbreviation of pekerjaan rumah, literally house work, but in school context it means homework.
It’s extremely common and natural in spoken and written Indonesian, including in fairly formal contexts like school and news about education.

Saying pekerjaan rumah for homework sounds more formal and is less common in everyday speech; people almost always just say PR.

Why is there no word like sudah or telah to mark the past tense before selesai?

Indonesian usually does not mark tense the way English does. Time is shown by context words such as tadi malam (last night).
Saya selesai mengerjakan PR tadi malam is already clearly in the past because of tadi malam.

You can add aspect markers if you want to emphasize completion:

Saya sudah selesai mengerjakan PR tadi malam. (quite natural)
Saya telah selesai mengerjakan PR tadi malam. (more formal/written)

But they are not required for the sentence to be correct and clear.

What’s the difference between tadi malam and malam tadi?

Both tadi malam and malam tadi can mean last night (the night that has just passed).
In practice:

tadi malam is the more common fixed expression for last night.
malam tadi is also correct but can feel a bit more like that night just now / earlier tonight, depending on context.

In your sentence, tadi malam is the most natural and neutral choice.

What does walaupun mean here, and how is it different from meskipun?

Walaupun means although / even though and introduces a contrast between two clauses.
In your sentence, it links I finished my homework last night with I often feel sleepy after work, showing that finishing the homework happened despite the sleepiness.

Walaupun and meskipun are almost interchangeable in modern Indonesian, especially in spoken language:

…, walaupun seringkali saya mengantuk setelah kerja.
…, meskipun seringkali saya mengantuk setelah kerja.

Both are fine; meskipun can sound slightly more formal in some ears, but the difference is small.

Is the comma before walaupun necessary, and can the sentence start with Walaupun instead?

Yes, the comma is normal because walaupun seringkali saya mengantuk setelah kerja is a subordinate clause.
You can also start with Walaupun and put the main clause second:

Walaupun seringkali saya mengantuk setelah kerja, saya selesai mengerjakan PR tadi malam.

This is just like English:

I finished my homework last night, although I often feel sleepy after work.
Although I often feel sleepy after work, I finished my homework last night.

Both orders are correct; it’s just a matter of emphasis and style.

Why is it walaupun seringkali saya mengantuk and not walaupun saya seringkali mengantuk? Is the word order important?

Both orders are grammatically correct:

walaupun seringkali saya mengantuk…
walaupun saya seringkali mengantuk…

The most common and neutral pattern is subject + adverb + verb:

walaupun saya seringkali mengantuk setelah kerja

Putting seringkali before saya is less common and can sound a bit more written or stylized. For everyday speech, walaupun saya sering (kali) mengantuk setelah kerja is the most natural.

What’s the difference between sering and seringkali in this sentence?

Both mean often.

sering = often (most common, neutral)
seringkali = often / frequently, sometimes a bit more emphatic or slightly more formal

In everyday conversation, sering is more common:

…, walaupun saya sering mengantuk setelah kerja.

Using seringkali is still correct; it can sound a bit more literary or just a bit stronger: very often.

Is mengantuk a verb or an adjective? How does it work in saya mengantuk?

Mengantuk literally means to feel sleepy / to be sleepy.
In Indonesian grammar it behaves like a stative verb: it describes a state, but it fills the verb slot in the sentence.

So:

Saya mengantuk. = I am sleepy / I feel sleepy. (no extra verb needed)

You cannot say saya adalah mengantuk; you just use mengantuk itself as the predicate.
In casual speech, people often shorten it to ngantuk: saya ngantuk.

What is the difference between kerja and bekerja here, and why is it setelah kerja and not setelah bekerja?

Kerja can function as a noun (work, job) or as a verb (to work in informal speech).
Bekerja is the more explicitly verbal form (to work) and sounds a bit more formal.

Both are possible:

setelah kerja (after work) – very common in everyday speech, treating kerja like a noun.
setelah bekerja (after working) – slightly more formal; emphasizes the activity.

In casual conversation, setelah kerja is very natural.

Could you also say setelah pulang kerja or sesudah kerja instead of setelah kerja? Are setelah and sesudah different?

Yes, you can say:

setelah kerja
sesudah kerja

Setelah and sesudah are near-synonyms and almost always interchangeable, with only slight style differences.

You can also be more specific and say:

setelah pulang kerja = after coming home from work

That adds the idea of going home, not just finishing work.

Do I have to repeat saya in the second clause, or can I omit it?

You can omit it. These versions are all acceptable:

Saya selesai mengerjakan PR tadi malam, walaupun seringkali saya mengantuk setelah kerja.
Saya selesai mengerjakan PR tadi malam, walaupun seringkali mengantuk setelah kerja.

Dropping saya is very natural in Indonesian if the subject is clear from context.
Repeating saya sounds a bit more explicit or formal, but it’s not wrong.

What is the overall level of formality of this sentence? Would it sound natural in everyday conversation?

The sentence is neutral–formal and would sound natural in many contexts.
Features:

saya is neutral/formal; informal speech often uses aku or regional pronouns.
PR, kerja, mengantuk are all fine in everyday conversation.
The structure with walaupun is standard and not overly formal.

So you could use this with friends, classmates, teachers, or colleagues without it feeling strange.