Do the following steps: 1. Clean your using apps to free the RAM 2. Restart your device If those wouldn't work, check your touch screen and see if it is broken or exposed to water. In anyway you need to replace your touch screen.

Try to reboot your device. Switch it off and do not use for 10 minutes, this process will refresh the software which is installed on your device. After that switch it on again. If it doesn't work, it might be the problem of the OS. You have to connect it to you PC and repair the OS. If it still doesn't work, maybe the battery is dead. You have to replace your battery.