The standard service tool for this model is Flash loader 7.5.4 CSC v0.4 (or a similar Flash Loader version designed for the Infineon platform).
If you encounter issues during the process, consult these common fixes: Tool Not Detecting Phone
Samsung USB Driver for legacy phones (Windows 7/XP recommended; Windows 10 may work with compatibility mode). samsung gt-c3520 flash file and tool
The GT-C3520 utilizes a specific tool developed for its proprietary hardware platform. Flash Loader 7.5.4 (or Flash Loader 7.5.16)
Monitor the progress bar. The flashing routine takes roughly 3 to 7 minutes to write the binary, TFS, and CSC sectors. The standard service tool for this model is Flash loader 7
Extract the firmware zip file and the Flash Loader tool zip file into separate folders on your desktop. Step 2: Configure Flash Loader
Use a high-quality OEM cable to prevent accidental disconnection. Flash Loader 7
To ensure a stable connection during the process. Step-by-Step Flashing Guide
While keeping these keys firmly pressed down, insert the Micro-USB cable from the PC into the phone.
Try using a different USB cable or a different USB port (preferably a back port on a desktop PC).
Because the GT-C3520 is a , consumer software is very unreliable. If you have no experience with JTAG or DNF flashers, do not attempt this.