How to hard-reset/factory reset of Huawei P9 or How to fix factory setting of Huawei P9
Restore your phone to its factory settings if it crashes or is slow to respond.
Back up important data on your phone before restoring factory settings. Restoring factory settings will erase all personal data from your phone, including fingerprints,account information, downloaded applications, and application settings.
2 Touch Advanced settings > Backup & reset > Factory data reset.
3 Choose whether to format your internal storage, and then touch Reset phone.
Selecting Erase internal storage will delete all files on your internal storage, such as music and images. Proceed with caution.
4 Touch Reset phone to restore your phone to its factory settings. Your phone will restart automatically when the process is complete.