usually I can free space on the internal memory of the phone in this way: settings - memory - internal archive - cached data (translation from Italian, excuse me). with my current phone, Huawei CUN-L21 Android 5.1 EMUI 3.1 I can not do it. nothing happens with a tap. another problem is that I can not move apps on the sd card. the option is there, but it is disabled (lighter color). what is the real problem of my phone?