Hello, I want to upgrade my xiaomi Mi4 to Android M, and i know that i need to do Wipe Data on my phone. But i have some question about this: I must do Wipe Data after or before that i upgrade my Xiaomi with 6.1.28? Wipe data reset my gallery?(So delete photo and video) or my contacts?(all the number save on the phone) Or it delete only the app that i download on my phone? Thank So much.