My screen is black Tecno Spark 5

By just saying the screen is black, I can't tell which is the cause, because there are many different reasons:

1. If your phone has received fall damage, you'll most likely do a screen replacement.
2. If your phone has received water damage, take it to a repair center and do an ultraviolet bath
3. If you've fiddled with the brightness, try to change it, but you need a good memory.
4. Other reasons could be a defective backlight, loose connections, software errors, anything.