VBA faster calculating
Just a couple of things:


With ThisWorkbook.Worksheets(9)
Range(Cells(3, 13), Cells(3, 44)).Select



You miss a . here, should be .Range, without that your With doesn't have any effect.


  Selection.Calculate


Don't need to select before calculate, you could immediately do .Range(..).Calculate
(Is it really necessary in your logic to calculate before copy)


With Range(Cells(i, 13), Cells(i, 44))



Again, . is missing, should be .Range...


For i = 4 To n + 2
With Range(Cells(i, 13), Cells(i, 44))
.PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
.Calculate
.Value = .Value2
End With
Next i



Do you really need to do this in sequence?? You could just do:

.Range(Cells(3,13),Cells(3,44).Copy 
.Range(Cells(4,13),Cells(n+2,44).PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, SkipBlanks:=False
.Calculate
.Range(Cells(4,13),Cells(n+2,44).Value = .Range(Cells(4,13),Cells(n+2,44).Value2


You can also find some further tips here: https://stackoverflow.com/documentation/excel-vba/1107/vba-best-practices/5925/switch-off-properties-during-macro-execution#t=201706191115061969896