Angular 6 - Does not update parent class field in daughter class view

I try to make an api RESTfull with Angular 6 and Java, which must perform the CRUD operations, until now everything seems to work correctly, except to edit and insert in Employee and Auto.

The model is composed of 3 tables, Branch, Employee and Auto, each with its attributes and the foreign key.

Branch (id, name, description) Employee (id, first name, last name, ..., id_sucursal) Auto (id, name, description, ..., employee_id)

These are the methods by which I enter and edit on the backend

@Override
public String insertar(Auto auto) {
    String resultado = null;
    String sql = "INSERT INTO auto(nombre, descripcion, precio, placa, fecha_ingreso, marca, id_empleado) VALUES (?, ?, ?, ?, ?, ?, ?)";

    try (Connection cn = con.conectar();
        PreparedStatement pst = cn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);) {
        pst.setString       (1, auto.getNombre());
        pst.setString       (2, auto.getDescripcion());
        pst.setFloat        (3, auto.getPrecio());
        pst.setString       (4, auto.getPlaca());
        pst.setString       (5, auto.getFechaIngreso());
        pst.setString       (6, auto.getMarca());
        pst.setInt          (7, auto.getEmpleado().getId());
        pst.executeUpdate();

        ResultSet gk = pst.getGeneratedKeys();

        if (gk.next())
        {
            auto.setId(gk.getInt(1));
        }

        Gson gson = new Gson();
        resultado = gson.toJson(auto);

    } catch (Exception ex) {
        resultado = ex.getMessage();
    }

    return resultado;
}

@Override
public String editar(Auto auto) {
    String resultado = null;
    String sql = "UPDATE auto SET nombre= ?, descripcion = ?, precio = ?, placa = ?, fecha_ingreso = ?, marca = ?, id_empleado = ? WHERE id = ?";

    try (Connection cn = con.conectar(); PreparedStatement pst = cn.prepareStatement(sql);) {
        pst.setString(1, auto.getNombre());
        pst.setString(2, auto.getDescripcion());
        pst.setFloat(3, auto.getPrecio());
        pst.setString(4, auto.getPlaca());
        pst.setString(5, auto.getFechaIngreso());
        pst.setString(6, auto.getMarca());
        pst.setInt(7, auto.getEmpleado().getId());
        pst.setInt(8, auto.getId());
        pst.executeUpdate();

        JsonObject json = new JsonObject();
        json.addProperty("status", "exito");
        resultado = json.toString();
    } catch (Exception ex) {
        JsonObject json = new JsonObject();
        json.addProperty("status", ex.getMessage());
        resultado = json.toString();
    }

    return resultado;
}

And this method is responsible for doing both in the component

  createNewBranchOffice(){
if(this.validateNotEmptyField())
{
  this.refresh=false; 
    if(!this.isUpdate)
    {           
        this._branchOfficeService.insertSuc( { nombre : this.bOffice.nombre , descripcion : this.bOffice.descripcion } ).subscribe
        (
          (response :any) =>
          {
            this.bOffices.push(response);
            this.refresh=true;
            console.log(response);
            this.clear();
          }, 
          error => {
            console.log(error);
          }
        )
    }
    else
    {
        this.isUpdate = false;
        this._branchOfficeService.editSuc( this.bOffice.id, { nombre: this.bOffice.nombre, descripcion: this.bOffice.descripcion } ).subscribe
        (
          (response : any) =>
            {
              this.bOffices[this.index] = JSON.parse(JSON.stringify(this.bOffice));
              this.refresh=true;
              console.log(response);
              this.clear();
            },
              error =>
            {
              console.log(error);
            }
        )
    }
      this.refresh=false; 
}

}

And here is how I get them in the table

  <div>
            <div class="form-group"> <label>Name</label> <input type="text" class="form-control input-group-sm input-sm" [(ngModel)]="aut.nombre"></div>
            <div class="form-group"> <label>Descripcion</label> <input type="text" class="form-control input-group-sm input-sm" [(ngModel)]="aut.descripcion"></div>
            <div class="form-group"> <label>Price</label> <input type="text" class="form-control input-group-sm input-sm" [(ngModel)]="aut.precio"></div>
            <div class="form-group"> <label>Mat</label> <input type="text" class="form-control input-group-sm input-sm" [(ngModel)]="aut.placa"></div>
            <div class="form-group"> <label>Admision Date</label> <input type="text" class="form-control input-group-sm input-sm" [(ngModel)]="aut.fechaIngreso"></div>
            <div class="form-group"> <label>Mark Trade</label> <input type="text" class="form-control  input-xs" [(ngModel)]="aut.marca"></div>
            <div class="form-group">
                <label for="">Employees</label>
                <select [(ngModel)]="aut.empleado.id" class="custom-select">
                          <option selected >Select, please.....</option>
                          <option *ngFor="let emp of emps" [ngValue]=" emp.id" > {{emp.nombre}} </option>
                </select>
            </div>
            <div class="form-group" style="display: none;"> <input type="text" class="form-control  input-xs" [(ngModel)]="aut.empleado.nombre"></div>
            <div class="form-group">
                <button (click)="createAuto()" class="btn btn-sm btn-success"><i class="fas fa-plus-square"></i></button>
            </div>
        </div>

This is a method when clicking on edit, which loads the data in the registration form

   editAuto(index){
 this.isUpdate=true;
 this.aut = JSON.parse(JSON.stringify(this.auts[index]));
 this.index = index;
}

The truth is that I am new to all this in both java, angular and use of json so I do not know what I could do to solve it without altering the model of the database And here below is the view, that when editing load in a form, and in the form I update the data and the changes are reflected except in the employee column that only shows them when reloading the page