to make it readable flash the main and FS and CUST corresponding to your phone
i reccommend to use XS++ NOTE:you backed up your GDFS .
(FLASHING will remove everything thats on your phone such as mobile games or pictures so make backup before you start!)
if your into contonese or use to traditional > flash it hong kong firmware
if your into manderine or use to simplified chinese > flash it CHINA firmware
all firmware comes with english language so you do not have to worry about that.
MAIN and FS must match when flashing and custpack must match the phone with the language you installed.
XS++ requires
usb installed (DCU-60 cable)
All other files such as xs++, main, fs, custpack can be found on this website.
bit of info what language in each packs contain:
Top Sony - Languages Description
hope this answers every question you need to know for now.