If mistake !

[Youssef]

Public Class login

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim usernam1 As String = "youssef"
        Dim usernam2 As String = "Mariam"
        Dim unknown As String = TextBox.Text
        Dim password1 As String = "hey"
        Dim password2 As String = "hi"
        Dim unknownp As String = TextBox2.Text

        If TextBox.Text = usernam1 Then
            Label3.Text = "Correct"
        ElseIf TextBox.Text = usernam2 Then
            Label3.Text = "Correct"
        ElseIf TextBox.Text = unknown Then

            Label3.Text = "Invaild username"

        End If
        If TextBox2.Text = password1 Then
            Label4.Text = "Correct"
        ElseIf TextBox2.Text = password2 Then
            Label4.Text = "Correct"
        ElseIf TextBox2.Text = unknownp Then

            Label4.Text = "Invalid Password"

        End If
        If showd() Then
            Me.Close()
        End If




    End Sub
    Private Function showd() As Boolean

        If youssef() Or Mariam() Then
            If MessageBox.Show("Do you want to continue?", "Question", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
                Calculator.Show()

            End If

        End If
        Return True


    End Function
    Private Function youssef() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "youssef" And TextBox2.Text = "hey" Then
            MessageBox.Show("Welcome Youssef", "Welcome", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If
        Return True

    End Function
    Private Function Mariam() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "Mariam" And TextBox2.Text = "hi" Then
            MessageBox.Show("Welcome Mariam", "Welcome", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If
        Return True


    End Function
End Class

I don't know what the **** is wrong with this part?

 Private Function showd() As Boolean

        If youssef() Or Mariam() Then
            If MessageBox.Show("Do you want to continue?", "Question", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
                Calculator.Show()

            End If

        End If
        Return True


    End Function

I want if function youssef or function Mariam then calculator form shows and if it's not youssef or mariam it just end the programme

[Youssef]

OKay I fixed it a bit but it also doesn't work :

  Private Function showd() As Boolean
        If youssef() Or Mariam() Then
            Label5.Text = "Done"
        Else : Label5.Text = "suck"
        End If

I made it to be a small example but if youssef function is ok it shows on label5.text "Done" and if it doesn't it also shows "done" I want it if it is not youssef or Mariam then label5.text = "suck"

[Youssef]

I discovered that the problem is with the function youssef and Mariam but I don't know why? because if I make it like this:

  If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "youssef" And TextBox2.Text = "hey" Then
            Label5.Text = "done"
        Else : Label5.Text = "suck"
        End If

and it worked but if I used the function it doesn't work !

[Youssef]

one more failure try:

   If fin() Then
            Me.Close()
        End If



    End Sub

    Private Function fin() As Boolean

        If youssef() Then
            Calculator.Show()
        ElseIf Mariam() Then
            Calculator.Show()
        End If

        Return True

    End Function
    Private Function youssef() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "youssef" And TextBox2.Text = "hey" Then
            MessageBox.Show("Welcome Youssef", "Welcome", MessageBoxButtons.OK, MessageBoxIcon.Information)


        End If
        Return True

    End Function
    Private Function Mariam() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "Mariam" And TextBox2.Text = "hi" Then
            MessageBox.Show("Welcome Mariam", "Welcome", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If
        Return True
    End Function

[Youssef]

Okay Last try and it worked:

If youssef() OrElse Mariam() Then
            Me.Close()
        End If



    End Sub


    Private Function youssefs() As Boolean

        If youssef() Then
            Calculator.Show()
        End If

        Return True

    End Function
    Private Function youssef() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "youssef" And TextBox2.Text = "hey" Then
            
            Calculator.Show()
        End If
        Return True
    End Function
    Private Function Mariam() As Boolean
        If Label3.Text = "Correct" And Label4.Text = "Correct" And TextBox.Text = "Mariam" And TextBox2.Text = "hi" Then
            Calculator.Show()
        End If
        Return True
    End Function

but I want the messagebox.show(etc etc) at the function youssef and Mariam

[Inferrd]

Going back to your original code:

Your youssef funtion tests if it is youssef who is logging in.
It should return True if it is youssef.
It should return False if it isn't youssef.

The logic should be something like:

PseudoCode

IF all labels = "Correct" and it is youssef THEN
Show welcome message
RETURN TRUE
ELSE
RETURN FALSE