I would like to use the NPC instead of returning a message, it executes a command example: /kit

You would need to find a plugin made to do that.
Example https://www.myvector.xyz/index.php?resources/talking-npc-vendors.4/

Adds customizable, human, non-player characters in-game. Make your cities a little bit more lively!

These NPC are no longer intended to be used to fight or shoot but to be utilized by other plugins.