VBA - Makro ist ungewöhnlich langsam

Sub Test()
Dim Zelle As Range
Dim Letzte As Long
With Application
.ScreenUpdating = False
.Calculation = xlCalculationManual
.EnableEvents = False
End With
With ActiveSheet.UsedRange
For i = .Rows.Count To 2 Step -1
If .Cells(i, 1) = "" Then
.Cells(i, 1).EntireRow.Delete
End If
Next i
End With
Letzte = ActiveSheet.UsedRange.SpecialCells(xlCellTypeLastCell).Row
For Each Zelle In ActiveSheet.Range("A1:A" & Letzte)
If Zelle.Value = "Buchungsdatum" Then
Zelle.EntireRow.Delete
End If
Next Zelle
ActiveSheet.Range("F1:F" & Letzte).Select
Selection.Replace What:="RST", Replacement:="Aufl. RST"
For Each Zelle In ActiveSheet.Range("G1:G" & Letzte)
Zelle.Value = Zelle.Value * (-1)
Next
Range("A1").Select
With Application
.ScreenUpdating = True
.Calculation = xlCalculationAutomatic
.EnableEvents = True
End With
End Sub