A. Since RAM is used on the operation system and the apps, the device of the SD card just can visit storage files with small room.
B. The storage of tablet is consisted by RAM andROM.Please do not put files in the Ram, kindly operate as following steps: Settings —-apps —download, then you can remove files to the SD card. Meantime, ROM just can distribute about 10%-20% to the OS. If you find room is shortage, kindly extend the SD card .