Realme doesn't give you the firmware because they know that you can root device.wait for sometime I will create twrp for our phone btw i can give you firmware links
Download Realme C25Y Firmware Firmware, (RMX3265, RMX3268, RMX3269) Flash File, Latest Stock ROM. flash your phone using realme flashtool or MSM Download tool.
It depends upon area ,you have to select global version but both firmware are same not even a single file difference if you don't want to take risk and
If you have wifi download both firmware for backup.