How to modify the firmware of a phone based on the SpreadTrum chipset?

Question

Mobile devices

They asked me to change the firmware on the phone, which is built on the SpreadTrum chipset. The phone is called Land Rover F8. I downloaded the official firmware, and it was in the form of a * .pac file. I found a program that allows you to load and view such files, but found only binaries (*.bin). Maybe someone has already tried to change the firmware of such phones and tell you where to dig? As I understand it, the firmware was definitely not written in a notepad, and the elements of the interface firmware can be extracted.