OnePlus 9 User's Manual

To take a screenshot on the OnePlus 9, press and hold the power button and the volume down button simultaneously until you see the screen flash. The screenshot will be saved in the Gallery app under Screenshots.
First, check the charging cable and adapter for any signs of damage. Try using a different charger if possible. Also, ensure the charging port on the phone is free of debris. If the issue persists, restart the device or perform a factory reset if necessary.
To enable Developer Options, go to Settings > About Phone, and tap on 'Build number' seven times. You will see a notification that Developer Options are enabled. You can access it in the main Settings menu.
To improve battery life, reduce screen brightness, limit background app activity, enable Battery Saver mode, and disable features like Bluetooth, GPS, and Wi-Fi when not in use. Additionally, update your apps and system software regularly.
Go to Settings > System > Reset Options > Reset Wi-Fi, mobile & Bluetooth. This will reset all network settings, including Wi-Fi passwords, mobile data settings, and paired Bluetooth devices.
Use the OnePlus Switch app to transfer data from your old phone. Install the app on both devices, follow the on-screen instructions to connect them, and choose the data you want to transfer.
To clear the cache, go to Settings > Storage > Cached data, and tap on Clear cache. Alternatively, you can clear the cache of individual apps by going to Settings > Apps & notifications > See all apps, selecting an app, and tapping on Storage & cache > Clear cache.
If your OnePlus 9 is overheating, remove any case that might be trapping heat, and avoid using it while charging. Close unnecessary apps running in the background, reduce screen brightness, and ensure the device is running the latest software updates.
To set up Face Unlock, go to Settings > Security & lock screen > Face Unlock. Follow the on-screen instructions to add your face data. Once set up, you can use Face Unlock to unlock your phone quickly.
To enable dark mode, go to Settings > Display > Dark Mode. You can turn it on manually or set it to activate automatically based on the time of day.