uml – C # variables in the sequence diagram

I play with the sequence diagram. And the main question is how to correctly draw the interaction of the sequence diagram with the variable. How to draw

1) when Make a payment aggregates the person

insurance.MakePayment (person.FirstName, person.SecondName, 20);

2) Variable assignment

internalVariable = SecondName;

I'm not sure to draw the right sequence.

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Example of namespace
{
public class person
{
public string FirstName {get; together; }

public string SecondName {get; together; }

public channel Salary {get; together; }
}

public class insurance
{
Private Bank readonly Bank;

public insurance ()
{
bank = new bank ();
}

public bool MakePayment (string FirstName, string SecondName, value int)
{
if (bank.GetBalance (FirstName, LastName)> value)
{

}
return true;
}
}

public bank
{
SomeVariable private string {get; together; }

private string internalVariable;

public bank ()
{

}

GetBalance public decimal (FirstName string, SecondName string)
{
SomeVariable = First Name;
internalVariable = SecondName;
returns 320;
}
}

class program
{
static void Main (string[] args)
{
Person person = new person ();
person.FirstName = "First Name";
person.SecondName = "SecondName";
Insurance insurance = new insurance ();
insurance.MakePayment (person.FirstName, person.SecondName, 20);
PrintResult (person.FirstName);
}

public static void PrintResult (string firstName)
{
Console.WriteLine (firstName);
}
}
}