@yingchun: I see what you mean. As a starting point I recommend moving the internally stored images to your SD card. To do this, go to Apps > My Files > Images > Select a folder > Tap the 3 dots in the top right > Edit > Tap the images you want to move, or hit 'All' in the top left > Move > Back > SD card > Move here. Repeat this action for all folders, and this will free up a decent chunk of memory for you. Hope this helps.