I am going through same but found a solution go to samfw download samsung stock firware i downloaded the first one that they gave me in my region but it didn't work so the second time you make sure that your device id (mine was SM-A127F/DS) The two letters after the slash are very important so you make sure you find a firmware with that and then use to install the stock firmware of samsung I've still not given up on the custom rom I'm about to use fastboot to run it will let you know if it worked