Learn Hardcore Indonesian: Saku jaket saya penuh kertas; saya menghapus catatan yang tidak penting. - My jacket pockets are full of papers; I delete the notes that are not important.

No. You can make the pocket the subject: Saku jaket saya penuh kertas. If you want a locative construction, use Di saku jaket saya ada banyak kertas (“In my jacket pocket there is a lot of paper”). Avoid “Di saku … penuh kertas” without a subject; it’s more natural with ada or by keeping saku as the subject.

Why is it “saku jaket saya” and not “saku saya jaket”?

Indonesian possession is head-first. Here the head is saku (pocket), and it’s possessed by jaket saya (my jacket): [saku] [jaket saya] = “the pocket(s) of my jacket.” You can also say saku jaketku (my jacket’s pocket[s]) using the -ku possessive.

Is “saku” singular or plural here?

Number is usually unmarked. Saku can mean “pocket” or “pockets” from context. To be explicit:

Emphasize plural: saku-saku jaket saya or semua saku jaket saya
Emphasize singular: satu saku jaket saya

Is “penuh kertas” correct, or should it be “penuh dengan kertas”?

Both are acceptable.

penuh kertas is concise and common in speech.
penuh dengan kertas is slightly more explicit/formal.
penuh akan kertas is bookish. You might also see passive-like forms such as dipenuhi kertas (“is filled with paper”).

Do I need a classifier with “kertas”? How do I say “sheets of paper”?

Kertas can be a mass noun (“paper/papers”). If you want “sheets,” use the classifier lembar:

selembar kertas = a sheet of paper
beberapa lembar kertas = several sheets of paper
lembaran-lembaran kertas = sheets of paper (plural emphasis)

Does “menghapus” mean “to delete,” “to erase,” or “to throw away”? Which fits best here?

menghapus = erase marks (on a page) or delete (digital)
membuang = throw away/discard (physical items) In a pockets-full-of-paper context, you probably mean discarding: saya membuang catatan yang tidak penting. Use menghapus if you’re erasing pencil/pen marks or deleting notes in an app.

What’s the difference between “menghapus” and “menghapuskan”?

menghapus = to erase/delete/remove writing or items (literal and common)
menghapuskan = to abolish/eliminate something abstract (taxes, debt, discrimination): e.g., menghapuskan pajak For notes, use menghapus, not menghapuskan.

What is “yang” doing in “catatan yang tidak penting”?

yang marks a relative clause: catatan yang tidak penting = “notes that are not important.” It selects a subset from a larger set. Without yang, catatan tidak penting can sound like a general classification (“unimportant notes” as a type), while yang highlights the specific ones you’re targeting.

Why “tidak penting” and not “bukan penting”?

Use tidak to negate adjectives and verbs; use bukan to negate nouns/pronouns.

tidak penting = not important (adjective)
bukan dokter = not a doctor (noun) So: catatan yang tidak penting, not bukan penting.

Can I drop “catatan” and just say “saya membuang yang tidak penting”?

Yes, if context makes the noun obvious. yang can nominalize a description, so yang tidak penting = “the unimportant ones.” Example: Saku jaket saya penuh kertas; saya membuang yang tidak penting.

Is the semicolon normal in Indonesian?

Yes. It functions like in English: joining two closely related independent clauses. In everyday writing you could also use:

A period: … penuh kertas. Saya …
A comma plus a connector: …, lalu/kemudian saya …

Do I need “adalah” before “penuh”?

No. With predicate adjectives, Indonesian doesn’t use adalah. Say Saku jaket saya penuh kertas, not Saku … adalah penuh kertas. adalah is mainly for equating noun phrases.

Can I use “aku” instead of “saya”? What about “-ku” for possession?

saya = neutral/formal
aku = informal
gue/gua = very informal (Jakarta) Possession:
jaket saya (neutral/formal)
jaketku (informal, with enclitic -ku)
jaket gue (very informal) Match pronouns and style consistently: Aku membuang catatan … / Saya membuang …

Is “saku” the only word for “pocket”? What about “kantong/kantung”?

saku = specifically a clothing pocket (most precise here)
kantong/kantung = pocket/bag/pouch (broader); common in compounds like kantong celana (pants pocket) or kantong plastik (plastic bag) In your sentence, saku is the best default.