Flashtool 0.9.18.2 by @Androxyde (lower versions may work to.)
XZDualRecovery by [NUT].
Current rooted FW version: 10.5.A.0.230.
SuperSU by Cainfire, integrated in system, FULL ROOT!
For locked bootloaders.
Unlocked may try also.
How to update to 10.5.1.A.0.283:
Download 4.4.4.flashable.zip (920MB) and C6603_10.5.1.A.0.283.ftf (17MB)
Put 4.4.4.flashable.zip on (the external) SDcard1;
Put C6603_10.5.1.A.0.283.ftf inside the Flashtool/firmwares folder;
Create a backup of your phone in TWRP/CWM.
Flash 4.4.4.flashable.zip in TWRP/CWM
NOTE: do not reboot but go back to the main menu, then go to reboot->power off;
Flash everything in C6603_10.5.1.A.0.283.ftf using flashtool;
Reboot to system.
The first boot will be slow and after some time at the boot animation you will see Android start optimizing the apps on your phone.
I want to thank [NUT] for is help and Guide,and also Rajeev for is help to!
P.S.- This firmware is from Portugal,so expect apps that you wont need,so delete them
Try this at your own risk,i am not responsible if anything bad happens!