Mods doesn't run so well

Hi fellow officers.

As the title says mods doesn't go as planned. For example, I downloaded an official sierra mod which bring new guns in the game, but after pasting the zip where it goes, turning it on and launch the game it doesn't work, other are like more officers, female swat and other...none of them work. Is there a fix for that or is something very odd to happen?

Note: I've played Custom and Lan, none of them do anything