Hey,
A simple look through reforger's wiki would answer your questions. Here are I think useful links:
ABOUT JSON: https://community.bistudio.com/wiki/Arma_Reforger:Scripting:_JSON
ABOUT SERIALISATION: https://community.bistudio.com/wiki/Arma_Reforger:Serialisation
JSON API STRUCT: https://community.bistudio.com/wiki/Arma_Reforger:JsonApiStruct_Usage
Using REST may also come in handy: https://community.bistudio.com/wiki/Arma_Reforger:REST_API_Usage
Im new to reforger modding so if I overlooked something or understood your question incorrectly sorry 'bout that. GLHF