Oppo
Change System Language on Oppo auf Oppo
On Oppo phones running ColorOS, the system language option is not on the first Settings screen. It is grouped together with region and input settings, which is why many users overlook it after a factory reset, a second-hand purchase, or a SIM card swap that triggers a language change.
Since ColorOS builds on regular Android, it inherits the same full language list as other Android phones. The interface, however, organizes these options under an additional settings group instead of showing them directly in the main menu.
To switch the language, go to Tap on Settings ➔ Tap on Additional settings ➔ Tap on Language & region ➔ Tap on Add a language ➔ Choose a Language. After picking the language you want, drag it to the top of the list with Drag the Language to the first position, then confirm with Tap on Change to....
Dragging the new language to the first position matters, because ColorOS always applies whichever language sits at the top, not just the one you last selected. If several languages remain in the list, the phone keeps the previous one active until you reorder them.
Some pre-installed apps may keep using their own language setting even after you change the system language, especially apps that offer an in-app language switch. In that case, check the language option inside the specific app separately.