what you need is flash it in google can find this program is called flashtool, then enters xda developers and go to the section xperia sp and part of android development find your model and the stock rom, and then you install the flashtool go to where you installed (open my pc and then your hard drive and there you will be the flashtool folder) and find the firmware folder and there you put the rom stock you downloaded and then open the flash give it the button that has a flash and you das flash mode and choose the rom, then turn off the cel and you press the lower volume key and connect it to the pc and voila, Czech videos on youtube for you guies