After the flashing process is complete:

You forgot to check WIPE USERDATA in Flashtool. Fix: Repeat the process, ensuring USERDATA is ticked.

Would you like a step-by-step guide for creating or finding the correct G3311 FTF file?

If you prefer an official method without manual FTF files, use the Sony Xperia Companion Software Repair and follow the prompts to "repair" the device.