Before downloading this application, keep in mind that your device must have "root" access. If you don't know what that is, first do some research and find out. You will need another application to grant root access, like Kingroot, for example.
Android 4.4 KitKat does not allow the system to modify the files contained on the SD card. SDFix restores this possibility by modifying an Android configuration file. As mentioned before, for this to be possible, you must have "root" access. After making the changes, it is necessary to restart the device for the changes to take effect.