How to add items into cart in a food delivery app

Hi All,

        I'm developing a mobile application. Here I'm getting data from swagger rest API. So after clicking on a particular restaurant the items specific to that restaurant will appear. As there is no button to increment decrement like this (+0-) I have downloaded a number increment button module and used it in my app. Here to add items into cart I have writen logic where when the user clicks on an item down left corner it will display 1 item added or 2 items added, but it is working only for one particular item.  When the user will click on another one that value is getting overridden and displaying that latest value but not the total number of items. Hope you guys get my point and please help me with this.


Can you attach the .oml file or print screens with or logic?