Learn Hardcore Indonesian: Guru menekankan bagian paling penting di awal presentasi. - The teacher emphasizes the most important part at the beginning of the presentation.

Root: tekan (press, put pressure on)
Prefix: meN- (active voice) → initial t drops: tekan → menekan
Suffix: -kan (causative/applicative) → menekankan “to put emphasis on something” Note: menekan without -kan is “to press/pressure; to suppress,” not “to emphasize.”

Is menekankan transitive? Do I need a preposition after it?

Yes, it’s transitive and can take a direct object: menekankan [noun phrase]. You’ll also see:

menekankan pada [noun] (very common, especially in writing)
With recipients: menekankan kepada [people] (e.g., “to the students”) Avoid: menekankan ke [noun] for people; use kepada.

Can I use a clause after it, like “that …”?

Yes. Use bahwa:

Guru menekankan bahwa … = “The teacher emphasized that …” You can also use an object noun phrase: menekankan pentingnya … (“emphasized the importance of …”).

Is bagian paling penting okay without yang, or should it be bagian yang paling penting?

Both are correct. Bagian paling penting is concise and natural; bagian yang paling penting can feel a tad more explicit/clear in longer sentences. Meaning is the same.

Can I say bagian terpenting instead of bagian paling penting?

Yes. Terpenting and paling penting both mean “most important.” Terpenting can feel slightly more formal/literate, but both are very common.

Does di awal presentasi modify the verb (time) or the noun (bagian)?

By default it’s read as a time phrase modifying the verb (“at the beginning of the presentation”). If you want to say “the part at the beginning,” make it explicit:

“the part at the beginning of the presentation”: bagian awal presentasi or bagian pada awal presentasi
To make the time adverb crystal clear, front it: Di awal presentasi, guru menekankan …

Which is better here: di awal or pada awal?

Both are acceptable. Pada awal is a bit more formal; di awal is extremely common in everyday speech and writing. In very formal prose, some prefer pada for time expressions.

Can I move the time phrase to the front?

Yes: Di awal presentasi, guru menekankan bagian paling penting. A comma is customary after fronted time/place phrases.

How would I say this in the passive voice?

Use ditekankan:

Bagian paling penting ditekankan (oleh) guru di awal presentasi.
Or front the time phrase: Di awal presentasi, bagian paling penting ditekankan guru. Including oleh is optional and more formal.

How do I show past, habitual, or future time?

Use time words/aspect markers (Indonesian has no tense inflection):

Past/completed: tadi, kemarin, sudah/telah (e.g., Guru sudah menekankan …)
Habitual: sering, biasanya, selalu
Future: akan, nanti, a future time adverb (e.g., Besok guru akan menekankan …)

Does guru mean “a teacher” or “the teacher” here?

Context decides. Bare guru can be either. To force “a teacher,” use seorang guru. To make it clearly definite, use guru itu or gurunya (“that/the teacher”).

Should it be presentasi or presentasinya?

Both are possible:

presentasi = “a/the presentation” (context decides)
presentasinya = “the/that presentation” (definite, known) or “his/her presentation” (possessive), depending on context.

Any quick pronunciation tips for the words?

guru: GOO-roo (g always hard)
menekankan: mə-nə-KAN-kan (e like schwa; stress typically near the end)
bagian: ba-GEE-an (g hard; “gi” = gee)
paling: PAH-ling (ng as in “sing”)
penting: pən-TING
di awal: dee AH-wal
presentasi: prə-zen-TAH-see (s as in “see”)

Are there handy synonyms for bagian and for “emphasize”?

For “part/section”: bagian (section), poin (point), aspek (aspect), inti/pokok (gist/core).
For “emphasize”: menekankan, menggarisbawahi (underscore), menitikberatkan (put weight on), menonjolkan/menyoroti (highlight), menegaskan (assert/clarify).

Is the spacing in di awal correct, or should it be written together?

Correct as two words. The preposition di is always written separately: di awal, di rumah, di sekolah (not “diawal,” “dirumah,” “disekolah”).