Opóźnij funkcję na WinForm

//Your window Constructor
public MyWindow()
{
    InitializeComponent();

    this.Cursor = Cursors.WaitCursor; 
    this.Enabled = false;
    WaitSomeTime();

    //load stuff
    .....
}

public async void WaitSomeTime()
{
    await Task.Delay(5000);
    this.Enabled = true;
    this.Cursor = Cursors.Default; 
}
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