Learn Hardcore Indonesian: Titipan kamu aman; saya mengurusnya sampai kamu kembali. - Your deposited item is safe; I will take care of it until you return.

Indonesian doesn’t use a verb “to be” in present-tense equational sentences. Adjectives can serve as predicates. So Titipan kamu aman literally reads “Your entrusted item safe,” which means “Your entrusted item is safe.”

What exactly does titipan mean and how is it formed?

Base verb: titip = to entrust/leave something with someone (for safekeeping, delivery, etc.).
Noun with -an: titipan = the item/thing that has been entrusted, or the act/arrangement of entrusting.
It can be tangible (bag, key) or intangible (a message: titip salam “send my regards”). Context decides which.

Should it be titipan kamu or titipanmu?

Both are correct.

titipan kamu = separate pronoun; neutral and clear.
titipanmu = clitic -mu; a bit tighter/more informal and common in writing too. Style choice. Many speakers prefer titipanmu for brevity.

What does the -nya in mengurusnya refer to?

It’s the third-person object clitic meaning “it/him/her.” Here it refers back to the entrusted item (titipan). So mengurusnya = “take care of it.” It does not mean “your”; that would be -mu.

Why use mengurus here? Would menjaga or menyimpan be better?

mengurus = handle/manage/take care of (can include arrangements, logistics, admin).
menjaga = guard/watch over (focus on protection).
menyimpan = store/keep. Use depends on nuance. If you mean overall handling until return, mengurus works. If it’s mainly guarding the item, menjaga is fine; if you’re storing it, menyimpan also fits.

Do I need akan to show the future (e.g., “I will take care of it”)?

No. Indonesian is tenseless; future time is inferred from context. sampai kamu kembali (“until you return”) already implies a future span. Adding akan (saya akan mengurusnya) is fine but optional.

Is the semicolon (;) natural in Indonesian?

It’s acceptable and used similarly to English, but less common in everyday writing. A period or a comma would also be natural:

Titipanmu aman. Saya (akan) mengurusnya sampai kamu kembali.
Titipanmu aman, saya (akan) mengurusnya sampai kamu kembali.

Can I say saya urus instead of saya mengurusnya?

Yes. With pronoun subjects, Indonesian often uses the bare verb:

Biar saya urus (sampai kamu kembali).
Akan saya urus (sampai kamu kembali). All are natural. mengurusnya is a fully formed transitive verb with the object clitic; saya urus is concise and common.

What’s the difference between sampai and hingga?

They’re near-synonyms meaning “until.” sampai is more common in speech; hingga can feel slightly more formal/literary. sampai dengan is also used (esp. in notices) but here plain sampai is perfect.

Why use kembali and not balik or pulang?

kembali = return/come back (neutral, general).
balik = come back/go back (colloquial).
pulang = go/come home (specifically “home”). If the idea is simply “until you’re back,” kembali is safest. With friends you could say balik. If you mean “until you get home,” use pulang.

Is kamu polite here? Should I use Anda?

kamu = neutral/informal to peers or younger people; fine among friends/equals.
Anda = polite/formal to customers/strangers.
Address terms like Bapak/Ibu/Kak/Mas/Mbak + name are also common for politeness. Match the pronoun to the relationship and setting.

How would I make it more formally polished overall?

You could write:

Titipan Anda aman; akan saya urus sampai Anda kembali.
Or split with a period: Titipan Anda aman. Akan saya urus sampai Anda kembali.

Can I use the passive voice?

Yes:

Titipanmu aman; akan diurus sampai kamu kembali.
Or agentful passive: Titipanmu aman; akan saya urus sampai kamu kembali. Both are natural; the second explicitly marks the agent (“I”).

Is there any difference between mengurus and mengurusi/menguruskan?

mengurus and mengurusi are both widely used to mean “take care of/handle.” Many speakers use them interchangeably.
menguruskan often means “handle something for someone (on their behalf).” In your sentence, any of mengurus, mengurusi, or menguruskan (→ menguruskannya) would be understood; mengurus is the most neutral.

Could I add lagi after kembali?

Yes. sampai kamu kembali lagi is common in speech and adds a casual “again.” It’s optional; kembali alone is perfectly fine.

How would I negate parts of this sentence?

Predicate adjective: Titipanmu tidak aman = “Your entrusted item is not safe.” (Use tidak with adjectives/verbs.)
Time-aspect: belum = “not yet”: Titipanmu belum aman.
Verb negation: Saya tidak (akan) mengurusnya… Use bukan to negate nouns/pronouns, not used with aman here.