Sub CombineSheet()
    Dim arr, shtCount%, i&, t
    shtCount = Sheets.Count
    Application.ScreenUpdating = False
    t = Timer
    Sheets(1).Cells.ClearContents
    For i = 2 To shtCount
        With Sheets(i)
            arr = .Range(.Range("a7"), .Cells(.UsedRange.Rows.Count, .UsedRange.Columns.Count))
        End With
        Sheet1.Range("a" & Cells.Rows.Count).End(3).Offset(1, 0).Resize(UBound(arr), UBound(arr, 2)) = arr
    Next
    Application.ScreenUpdating = True
    MsgBox Timer - t
End Sub