Download The Stock rom For the Tecno Spark 4.
FIRMWARE
Android Version : 9 Pie
Model : KC8 MT6761
File Size : 2GB
HOW TO FLASH
Download the stock Tecno Spark 4 Firmware From the link below.
Download and Install MediaTek Drivers.
Use the SP flash tool to flash your phone.
See Full Guide On How to Flash MediaTek.
DOWNLOAD LINK