How can i do this effect?

[evren]

how can i do random shapes just like this?

 

[IamSam]

With a custom brush. The image is so small so it's hard to tell, but probably a texture or splatter style brush.

 

[IamSam]

Perhaps a sponge texture brush like this: https://www.brusheezy.com/brushes/2165-sponge-brushes-high-resolution

 

[evren]

that looks good thx