Saya mengganti tirai kamar karena tirai lama sudah kusam.

to be

Breakdown of Saya mengganti tirai kamar karena tirai lama sudah kusam.

• saya: I
• karena: because
• kamar: the room

Questions & Answers about Saya mengganti tirai kamar karena tirai lama sudah kusam.

What exactly does "mengganti" mean here—“to change” or “to replace”?

It means “to replace” (swap out the old item for a new one). If you say mengganti tirai, you’re replacing the curtains. Use mengubah for changing a property (e.g., the color) without swapping the item itself.

What’s the difference between "mengganti" and "menggantikan"?

• mengganti X (dengan Y): You, the doer, replace X (optionally state the new item with dengan). Example: Saya mengganti tirai lama dengan tirai baru.
• menggantikan X: The subject is the substitute that replaces X. Example: Tirai baru menggantikan tirai lama. Avoid forms like Saya menggantikan tirai lama dengan tirai baru in careful/formal usage; many people say it, but standard grammar prefers the two patterns above.

Can I just say "ganti" instead of "mengganti"?

Yes. In everyday speech, ganti is very common: Saya ganti tirai kamar. Mengganti is neutral-to-formal; ganti feels more casual/colloquial.

Do I need "dengan" to mention what I replaced the curtains with?

Yes, use dengan to introduce the replacement: Saya mengganti tirai kamar dengan tirai baru. Without dengan, if you name both items, it sounds incomplete. Another option is two sentences: Saya mengganti tirai kamar. Tirai barunya warna krem.