Hello, I want to buy this phone, but I'm avare of it screen, because I can't find any information about it strenght. Do it have gorilla glass or something like that? If it brakes it is still usefull or not? Because I Have zte nubia z9 mini and it screen is very weak, i break 3 screens now, and if top layer is cracked, so touch didn't work anymore. So I need to know if it is useful with top layer broken, like iphones? Thank you!