Parse a document with Painless

Hello,

In my index i have the field http.request.body.original (see also image below):

{"customerNr":"9203521","sendMethod":"TOUR","partialDelivery":false,"isTourTimetable":false,"deliveryAddressId":"8100000000000154802","items":[{"articleId":1001440486,"quantity":1},{"articleId":1001532184,"quantity":1}]}

Can someone provide me a painless script so that i can parse the previous doc in the following form below:

customerNr: 9203521
sendMethod: TOUR
partialDelivery: false
isTourTimetable: false
deliveryAddressId: 8100000000000154802
item1: 1001440486
quantity1: 1
item2: 1001532184
quantity2: 1

Thank you a lot in advance

This question has been asked before here: How to convert a json format string to json object using painless script kibana