Learn Hardcore Indonesian: Guru meminta saran lagi; mestinya kami menulisnya di kertas. - The teacher asks for suggestions again; we should have written them on paper.

Here lagi means again or more (of something). So Guru meminta saran lagi = “The teacher asked for advice again / asked for more advice.”

Placement: Put lagi after the object or right after the verb: meminta saran lagi is the most natural. If you say lagi meminta, it shifts meaning to “is currently asking” (progressive), not “again.”

Is meminta saran correct, or do I need meminta untuk saran?

Use meminta saran. Don’t insert untuk before a noun. If you want to ask someone to do something (a clause), use meminta agar/supaya + clause (e.g., Guru meminta agar kami menulisnya). Meminta untuk + verb is heard but less standard.

Why is there a semicolon? Could it be a comma or a period?

A semicolon links two closely related independent clauses. You could also use a period: Guru meminta saran lagi. Mestinya kami menulisnya di kertas. A comma alone is not ideal. You can add a connector for clarity: …, jadi mestinya… / …, makanya…

What does mestinya mean, and how strong is it compared with harus, mesti, seharusnya, and sebaiknya?

harus / mesti = must, obligation.
seharusnya / mestinya = should/ought to (normative expectation, often with mild criticism or regret). Mestinya is a bit more colloquial than seharusnya.
sebaiknya = it would be better to (soft advice).

Does mestinya mean “should have” (past) or just “should” (present)?

It’s neutral about time; context decides. To make “should have” clear, add a past-time cue:

Mestinya kami tadi menuliskannya di kertas.
Seharusnya kami sudah menuliskannya di kertas.

Why kami and not kita?

Kami = we (excluding the person you’re talking to). Kita = we (including the addressee). Use kami if the listener isn’t part of the group that should write it; use kita if they are.

What does the -nya in menulisnya refer to?

-nya is a third-person clitic (“it/him/her” or “the”). Here it most naturally refers back to saran (“write it down”). Without -nya, menulis di kertas just says “write on paper” without specifying what is being written.

Should it be menulisnya, menuliskannya, or menulisi?

menulis = to write (neutral). Menulisnya = write it.
menuliskan can emphasize the written content or add a benefactive sense. Menuliskannya (di kertas) is also fine and a bit more formal/emphatic.
menulisi means “to write on/cover (a surface) with writing” (e.g., menulisi dinding). Not appropriate for “write the suggestion.”

Why di kertas and not di atas kertas or pada kertas?

di kertas is common and perfectly natural for “on paper.”
di atas kertas is more literally “on top of the paper” and is also used, including for the idiom “on paper (in theory).”
pada kertas sounds stiff/odd here.
Don’t use ke kertas; ke is directional (“to”), not location.

Do I need a classifier like selembar (a sheet) before kertas?

Not required. Use it only if you want to specify a single sheet: di selembar kertas = “on a sheet of paper.”

Could I drop -nya and just say menulis di kertas?

Yes, but then you’re not specifying what is written. Menulisnya/menuliskannya di kertas explicitly means “write it on paper.”

Does Guru mean “the teacher” or “a teacher”? How do I make it definite?

Indonesian has no articles, so guru can be “a/the teacher” from context. To make it clearly definite, use guru itu or gurunya. Titles like Pak Guru / Bu Guru are also common when referring to a specific teacher.

How do I say who the teacher asked for advice from?

Add a recipient/source phrase:

Guru meminta saran kepada kami. (standard, “asked us for advice”)
Guru meminta saran dari kami. (emphasizes “from us” as the source) Both are acceptable; kepada is the more typical pattern with meminta [noun] kepada [person].

Could I use a passive to sound more natural?

Yes: Mestinya (saran itu) ditulis di kertas. This is generic and sounds like a rule: “The advice should be written on paper.”

Any spelling or morphology pitfalls here?

di as a preposition is separate: di kertas, not “dikertas.”
menulis is from meN- + tulis (the initial t drops: meN + tulis → menulis).
meminta is meN- + minta (m stays: mem-).
-nya attaches to the verb: menulisnya / menuliskannya.

Can I use kembali instead of lagi?

Often yes. Guru meminta saran kembali is more formal and means roughly “once again.” Lagi is more neutral/colloquial.