This app icon looks like the profile of a blue bird, and you'll find it on your Home screen, in the app drawer, or by searching. Log in if prompted. You'll see either of these at the top left of your screen. A menu will drop down. A new window will load. This is usually the first listing in the menu, located under your @username. You'll find this at the bottom of the page under "Log out." This is under the wall of text that explains what else you can do before deactivating your account like changing your @username and email if you want to use them again or downloading your Twitter data. To change your @username, edit the current name in "Settings and privacy." If you delete your account before changing your @username, you nor anyone else can use it in the future. When prompted, type the password that you use to log into Twitter into the "Password" text field. You'll see this dark pink button under the text field where you entered your password. Clicking this deactivates your account, though you can log back into your account any time in the next 30 days to restore it. Twitter will hold onto your account information for 30 days after deactivation, after which point your account will be gone with no chance of recovery.

TL;DR in Indonesian:
Buka Twitter. Sentuh foto profil atau ☰. Sentuh Settings and privacy. Sentuh Account. Sentuh Deactivate your account. Sentuh Deactivate. Masukkan kata sandi akun. Sentuh Deactivate.