How do I update the selected row in the listbox?

Hello so I have a Userform that has a listbox. When a user clicked a value from the listbox, it will be displayed on the corresponding comboboxes below, thus allowing the user to edit the value and update the row by selecting the Update Button.

mew.PNG

Sadly, I couldn't make that work and i'm going nuts. It's my first time to create a userform.

Here's my pathetic code and yes I don't have a code for Update button

     Private Sub btnDelete_Click()
    
        Dim a As Integer
            
            If MsgBox("Are you sure you want to delete this row?", vbYesNo + vbQuestion, "Yes") = vbYes Then
            
                For a = 1 To Range("A100000").End(xlUp).Row
                    If Cells(a, 1) = listHeader.List(listHeader.ListIndex) Then
                    Rows(a).Select
                    Selection.Delete
                End If
            Next a
        End If
    
    End Sub
    
    Private Sub btnView_Click()
    
        listHeader.RowSource = "A4:H1000"
    
    End Sub
    
Private Sub cmbAdd_Click()
    Dim sheet As Worksheet
    Set sheet = ThisWorkbook.Sheets("PRESTAGE DB")
    
    nextrow = sheet.Cells(Rows.Count, 1).End(xlUp).Row + 1
    
    sheet.Cells(nextrow, 1) = Me.cmbSchema
    sheet.Cells(nextrow, 2) = Me.cmbEnvironment
    sheet.Cells(nextrow, 3) = Me.cmbHost
    sheet.Cells(nextrow, 4) = Me.cmbIP
    sheet.Cells(nextrow, 5) = Me.cmbAccessible
    sheet.Cells(nextrow, 6) = Me.cmbLast
    sheet.Cells(nextrow, 7) = Me.cmbConfirmation
    sheet.Cells(nextrow, 8) = Me.cmbProjects
       
End Sub

    Private Sub cmbUpdate_Click()
    
    
    End Sub
    
    Private Sub CommandButton5_Click()
        listHeader.RowSource = ""
    
    End Sub
    
    Private Sub listHeader_Click()
    
    Dim rngMyData As Range
    
        cmbSchema.Value = UserForm1.listHeader.Column(0)
        cmbEnvironment.Value = UserForm1.listHeader.Column(1)
        cmbHost.Value = UserForm1.listHeader.Column(2)
        cmbIP.Value = UserForm1.listHeader.Column(3)
        cmbAccessible.Value = UserForm1.listHeader.Column(4)
        cmbLast.Value = UserForm1.listHeader.Column(5)
        cmbConfirmation.Value = UserForm1.listHeader.Column(6)
        cmbProjects.Value = UserForm1.listHeader.Column(7)
        
    
    End Sub