First/second image looks female, image with two looks like female on bottom and male above. Females look ready to mate when they want, but like someone else said, ghost shrimp are difficult to tell with and it can be a guessing game.
Once they start breeding, you notice their body shapes a bit better. The ones that look female that have a fleshy mass inside could be their saddle. Females also have more space between their spine and swimmeret area, where they carry the eggs once they have berried.
Objective_End5686 
does sexing matter when i think how they breed needs a specialized way?
First/second image looks female, image with two looks like female on bottom and male above. Females look ready to mate when they want, but like someone else said, ghost shrimp are difficult to tell with and it can be a guessing game.
Once they start breeding, you notice their body shapes a bit better. The ones that look female that have a fleshy mass inside could be their saddle. Females also have more space between their spine and swimmeret area, where they carry the eggs once they have berried.