You are in an advanced menu. Never flash a bootloader (CFE) unless you are 100% sure. A bad CFE = permanent brick without JTAG programmer. Stick to firmware-only upgrades.
(Most reliable)
To upgrade the firmware on your Huawei EchoLife HG520b , you must first obtain the correct firmware file, typically as an .iso or .bin image. You can then perform the upgrade through the router's web management page by navigating to the Maintenance section and selecting Firmware Upgrade Firmware Download Sources Huawei Echolife Hg520b Firmware Upgrade Download