how can i know if my application is Focused or not

In addition to the correct Solution 2:

An application cannot be "focused" or not.

"Focus" always means keyboard focus, when a control, only one at a time per interactive Windows session, can accept user input from a keyboard. You can only determine is the control presently in focus is owner by on of the windows of your application, as Solution 2 tells you. As the the window (form), it can be activated or not. When a window is activated, the control which was previously in focus, automatically gains the focus.

—SA

Use the Activated and Deactivate events of your main form...

Something like this:

Public Class MainForm

    Private hasFocus As Boolean = False

    Private Sub MainForm_Activated(sender As Object, e As EventArgs) Handles MyBase.Activated
        hasFocus = True
    End Sub

    Private Sub MainForm_Deactivate(sender As Object, e As EventArgs) Handles MyBase.Deactivate
        hasFocus = False
    End Sub

End Class

Good luck!