Press and hold buttons simultaneously.
Unzip the downloaded J250F firmware file. You will usually see four or five files starting with BL_ , AP_ , CP_ , CSC_ , and HOME_CSC_ . Boot into Download Mode: Power off your phone. samsung-j250f-u2-flash-file-firmware
Once finished, a green message will appear, and your device will automatically reboot. Press and hold buttons simultaneously
Ensure your phone has at least 50% charge to prevent it from powering off mid-flash. a green message will appear
Click the button and select the file starting with AP_ (this is the largest file and may take a moment to load). Click the CP button and select the file starting with CP_ .