makeing particles

how to make my owen particles script?

Why you want to write a script for your own particles?
Just in the hierarchy , click on create and on the top there’s the particle System.

Now see in the inspector there’s a lot of parameter’s you can play with.
Now you can add more functionality to your particle system by adding components to it.
click on the particle system in your hierarchy, then go to the component menu at the top,
Effects>Legacy Particles > Ellipsiod Particle Emitter
or Effects>Legacy Particles > Particle Animator
check this out: