How to get json response from wordpress website


I am developing an android app. I dont know anything about wordpress database or how to get data from the website. I googled for how to get data from the wordpress database I have got to know I could get json response from JSON API plugin of the wordpress. but It's hard for me to understand.

I am using food bakery theme for wordpress.

I just want to know how do I get required json response from this website. And where the data of products in that website is located in database.

for example : productcategories etc. etc

My expected response is something like this