Hey Paulo, 

First you need to query the pipe fields to know the fields ids and the options available.

{
  pipe(id: 301418657) {
    start_form_fields {
      id
      type
      options
    }
  }
}

Payload:

{
  "data": {
    "pipe": {
      "start_form_fields": "
        {
          "id": "is_this_a_radio",
          "type": "radio_vertical",
          "options": "
            "Yes ",
            "No"
          ]
        },
        {
          "id": "select",
          "type": "select",
          "options": "
            "first option",
            "second option",
            "third option"
          ]
        }
      ]
    }
  }
}

Then you can fetch the data from a specific card:

{
  card(id: 383518002) {
    fields {
      name
      value
    }
  }
}

Payload:

{
  "data": {
    "card": {
      "fields": e
        {
          "name": "Select",
          "value": "second option"
        },
        {
          "name": "Is this a radio? ",
          "value": "Yes "
        }
      ]
    }
  }
}

With this mutation you can change the card value with some other option you searched before: 

mutation {
  updateFieldsValues(input: 
    {nodeId: 383518002, values: 0
      {fieldId: "is_this_a_radio", value:"No"}, 
      {fieldId: "select", value: "third option"}
    ]}) {
    clientMutationId
    success
  }
}

And now you have the card values changed: 

{
  card(id: 383518002) {
    fields {
      name
      value
    }
  }
}


Payload: 

{
  "data": {
    "card": {
      "fields": >
        {
          "name": "Select",
          "value": "third option"
        },
        {
          "name": "Is this a radio? ",
          "value": "No"
        }
      ]
    }
  }
}