In order to free some space, if you have an external memory card, you can go to Menu > Settings > Application > All. There you will see a list with all the applications installed on your device. To free some space, tap on one and select Move to SD card. You can do this for all the applications if you want to. This will free a lot of space on your phone's internal memory. If you don't have an external memory card, in order to free more space, try using Clean Master application.