Read here : Flash K800 CID53 with K810 software CID53 (for begginers) - Top Sony Forums cos your phone CID is 53 and use these files as you should first debrand it and it's a good thing;
MAIN : K770_R8BA024_MAIN_GENERIC_VI_RED52
FS : K770_R8BA024_FS_CENT_EUROPE_RED52
custpack : HB1-06_Gen_CDA102568_207_R2A_GENERIC_CENT_EUROPE
and for unlocking read here : Patching CID53 (DB2020)DB2010,2012 - Top Sony Forums and to download the Simox SIM-lock gerator attached below to make the unlock patch