Does the window flicker due to loss of focus?

I have been working on a C # based Windows Forms application and I need some help. I am trying to recreate the flickering window that most Windows applications have when the form loses focus on the parent form. The best way I can explain is to open the calculator, open the help window and try to click on the calculator, the help window then flickers behind the calculator, losing and getting shading along the edges.

I managed to restore focus to the child window when the parent clicked, but this creates an odd flickering effect when the parent window instantly appears in front of the child window. I only guess, but this effect that I am looking for, apparently, is that the calculator never appears in front of the help window, and then the help window is simply activated and deactivated several times.

I tried to do some searches, and I saw several topics related to this, but none of the solutions match. I am new to creating windowed applications, so there are still things that I don’t understand, so be patient with me if I don’t understand at first.

Thank you in advance

Developing a calculator example:

1) open the calculator from the windows 2) on the toolbar, go to the help tab and open the calculator option 3) click on the calculator window 4) the calculator window will flicker, not lagging behind the calculator

The only progress I have made for this is

    private void MainForm_Activated(object sender, EventArgs e)
    {
        if (Open == true)
        {
            //blink active window

            _addForm.Activate(); //makes window active
        }
    }

An open variable is what I use to track open forms and becomes true when I show another form.