Phone overheating is a normal issue accompanied by heavy battery drain , happens every second day for me ! Just wen u feel the phone is overheating with battery drain just close the wazapp window by swiping down then try to launch it from the menu. By doing this at first it will not launch instead it'll crash completely instead of trying to recover using ur CPU & overheating the device, then after a minute or two launch it again from the menu and there u should hav it running normally !!! Don't know the technicalities behind it but it works !!!