How To parse Json in json

Hi , i am new to ELK and i wonder how can i parse json have json

For ex:
my "Content" field have String but this string is also a json

{
"Method":"some string",
"Request":"some string",
 "Time":"Datetime",
 "Content":
   "{
   "CustomerId":"int",
   "Code": "deneme",
   "Name": "string",
   "FirstName": "string",
   "LastName": "string"
   }"

How can i get the fields in "content" field and add them ? i mean my output should be :

{
 "Method":"some string",
 "Request":"some string",
 "Time":"Datetime",
 "CustomerId":"int",
 "Code": "deneme",
 "Name": "string",
 "FirstName": "string",
 "LastName": "string"
 }

See this thread.