I'm using huawei mate 8 and I'm willing to sell it but I need to delete my information from it permanently. ( photos, videos, contacts....)
I'm using Huawei Mate8 too, what you need to do for deleting information is to perform a "factory reset" of the device and then all of your phone data will be deleted from your Huawei Phone.
I would like to recommend encrypting your device before you are getting ready to wipe it. The encryption process will scramble the data on your device and, even if the wipe doesn't fully delete the data, a special key will be required to unscramble it.
To encrypt your device on stock Android, enter settings, click on Security, and select Encrypt phone. The feature may be located under different options on other devices. The next step is to perform factory data reset. Then would be kind of done already. If you are still concerned about the security, you can repeat the two steps above. To confirm it further, or you can download free data recovery software for Android to recover the data as to see if the software can restore them.