First look here
Top Sony - Languages Description and choose language,than you need
jdflasher (this is only free tool for flashing CID53 phones) and than choose firmware (MAIN and FS must be same version - R8BB001 exc.,FS choose based on your prefered language and CUSTpack must be same region like FS - EUROPE_2 ) or tell us what language you need and we tell you what files you need and you flash your phone like here
Flashing with jdflasher - Top Sony Forums