updating data

You need to use a!save() inside a saveInto to manipulate data.

a!localVariables(
  local!currentUserAccount : rule!PBY_getaccountbyid("test"),
  local!newBalance : 
  if(
    and(
      a!isNotNullOrEmpty(
        ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{e57ce205-d18d-4eb2-83ee-f669e5c56ab1}']
      ),
      a!isNotNullOrEmpty(
        local!currentUserAccount
      ),
      ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{e57ce205-d18d-4eb2-83ee-f669e5c56ab1}'] >= 0
    ),
    local!currentUserAccount + ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{e57ce205-d18d-4eb2-83ee-f669e5c56ab1}'],
    0
  ),

  local!typeValue: if(
    ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{7c7b6fd3-57be-4b83-8c0e-4e9ac46f0ed3}'] = "Virement interne",
    "Virement interne",
    if(
      ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{7c7b6fd3-57be-4b83-8c0e-4e9ac46f0ed3}'] = "Virement externe",
      "Virement externe",
      null()
    )
  ),
  a!formLayout(
    label: if(
      ri!isUpdate,
      "Update transaction",
      "Create transaction"
    ),
    contents: {
      a!columnsLayout(
        columns: {
          a!columnLayout(
            contents: {
              a!dropdownField(
                choiceLabels: {"Virement interne","Virement externe",},
                choiceValues: {"Virement interne","Virement externe",},
                label: "Type transaction",
                labelPosition: "ABOVE",
                placeholder: "Selectionner le type de virement",
                saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{7c7b6fd3-57be-4b83-8c0e-4e9ac46f0ed3}'],
                value : local!typeValue,
                searchDisplay: "AUTO",
                validations: {}
              ),
              /*a!textField(*/
              /*label: "Type Transaction",*/
              /*labelPosition: "ABOVE",*/
              /*value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}PBY transaction.fields.{7c7b6fd3-57be-4b83-8c0e-4e9ac46f0ed3}TypeTransaction'],*/
              /*saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}PBY transaction.fields.{7c7b6fd3-57be-4b83-8c0e-4e9ac46f0ed3}TypeTransaction'],*/
              /*characterLimit: 255,*/
              /*required: false*/
              /*),*/
              a!integerField(
                label: "Somme",
                labelPosition: "ABOVE",
                value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{e57ce205-d18d-4eb2-83ee-f669e5c56ab1}'],
                saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{e57ce205-d18d-4eb2-83ee-f669e5c56ab1}'],
                required: false
              ),
              a!textField(
                label: "Discription",
                labelPosition: "ABOVE",
                value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{ab543c07-1cb7-49d8-84a7-f62d36e9b438}'],
                saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{ab543c07-1cb7-49d8-84a7-f62d36e9b438}'],
                characterLimit: 255,
                required: false
              )
            }
          ),
          a!columnLayout(
            contents: {
              a!pickerFieldRecords(
                label: "Compte Utilisateur",
                labelPosition: "ABOVE",
                placeholder: "Select a Account",
                maxSelections: 1,
                recordType: 'recordType!{b37748b2-8103-41ea-8028-2b358e4f229c}',
                value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{30901144-d5a7-4d96-8411-68ef7cef8a04}'],
                saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{30901144-d5a7-4d96-8411-68ef7cef8a04}']
              ),
              a!dateTimeField(
                label: "Date",
                labelPosition: "ABOVE",
                value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{2f45e501-55aa-4cda-907f-cd99cf82e7cc}'],
                saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}.fields.{2f45e501-55aa-4cda-907f-cd99cf82e7cc}'],
                required: false
              ),
              /*a!pickerFieldRecords(*/
              /*label: "",*/
              /*labelPosition: "ABOVE",*/
              /*placeholder: "Select a User",*/
              /*maxSelections: 1,*/
              /*recordType: 'recordType!{4fd8023a-5200-4bb0-af2d-7bed73fb330b}PBY user',*/
              /*value: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}PBY transaction.fields.{692a0a51-d46d-4fee-a10e-aad2f90cb201}userId'],*/
              /*saveInto: ri!record['recordType!{ad2b45c4-cbc3-4de4-a189-c5593ad5032b}PBY transaction.fields.{692a0a51-d46d-4fee-a10e-aad2f90cb201}userId']*/
              /*)*/
            }
          )
        }
      )
    },
    buttons: a!buttonLayout(
      primaryButtons: {
        a!buttonWidget(
          saveInto: {
            a!save(
              target: local!currentUserAccount,
              value: a!update(local!currentUserAccount , 'recordType!{b37748b2-8103-41ea-8028-2b358e4f229c}.fields.{4a9de4b2-f127-44f1-86d2-21c2a6b2ee2d}', local!newBalance), 
            ),
          },
          label: if(ri!isUpdate, "Save", "Create"),
          submit: true,
          style: "SOLID",
          validate: true
        )
      },
      secondaryButtons: {
        a!buttonWidget(
          label: "Cancel",
          value: true,
          saveInto: ri!cancel,
          submit: true,
          style: "OUTLINE",
          validate: false
        )
      }
    )
  )
)

Thank you ! it works when i test  the interface  but not in the dataBase and the record 

Perfect! Happy to hear that hrshkar 

 thank  you ! But i want the data to be updated in my record base too

So that the "solde" displayed in my interface is the  correct solde after creating a transaction   

hrshkar  I would advice you to go through this documentation.

https://docs.appian.com/suite/help/24.1/recipe-use-the-write-records-smart-service-function-on-an-interface.html#:~:text=trigger%20the%20a!-,writeRecords()%20smart%20service%20function.,application%2C%20click%20NEW%20%3E%20Interface.

You have several ways of doing this but I would suggest you to use writeRecord().

thanks alot for your help yes i use writeRecord() but it update the field only  if i test it in the interface , if i do the test in my site the update is not working 

That shouldn't happen. Check your code properly.

Thank you so much for the solution.