Reinstalling without repartition of internal space
1.Download the app (assuming you have fastboot drivers installed), install it
2.Download the json file, put it inside the android folder and replace original one
3.Open the app and then refer to included screenshot for options, press the buttons:
A)1- select <b>Flash editor</b> mode
B)2- select the .json file from the android folder, we put it there previously
C)3- select <b>UPDATE</b> mode for firmware flashing
D)4- repeat all the options from the screenshot
E)5- and then press the <b>Start To Flash</b> button
Wait while rebooting process finishes, select android and have fun.
You might want to repartition only specific partitions like system/boot/recovery etc.