Untested, but this might do what you want:

Sub Update_New_Data_Completes()
    Dim Firstrow As Long
    Dim LastRow As Long
    Dim Lrow As Long

    Application.ScreenUpdating = False
   
    With ActiveSheet
        Firstrow = 2
        LastRow = .Cells(.Rows.Count, "A").End(xlUp).Row
        Dim dataset
        dataset = .Range(.Cells(Firstrow, "A"), .Cells(LastRow, "T")).Value
        For Lrow = LBound(dataset) To UBound(dataset)
            If Not IsError(dataset(Lrow, 1)) Then
                If dataset(Lrow, 19) Like "*COPIER*" Or dataset(Lrow, 19) _
                    Like "*REMOVE*" Or dataset(Lrow, 20) = "YES" Then
                        If dataset(Lrow, 10) <> "" And dataset(Lrow, 11) = "" Then
                            dataset(Lrow, 11) = "N/A"
                            dataset(Lrow, 12) = "N/A"
                            dataset(Lrow, 13) = "N/A"
                            dataset(Lrow, 14) = "N/A"
                            dataset(Lrow, 15) = "N/A"
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 10)
                        ElseIf dataset(Lrow, 11) <> "" And dataset(Lrow, 12) = "" Then
                            dataset(Lrow, 12) = "N/A"
                            dataset(Lrow, 13) = "N/A"
                            dataset(Lrow, 14) = "N/A"
                            dataset(Lrow, 15) = "N/A"
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 10)
                        ElseIf dataset(Lrow, 12) <> "" And dataset(Lrow, 13) = "" Then
                            dataset(Lrow, 13) = "N/A"
                            dataset(Lrow, 14) = "N/A"
                            dataset(Lrow, 15) = "N/A"
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 10)
                        ElseIf dataset(Lrow, 13) <> "" And dataset(Lrow, 14) = "" Then
                            dataset(Lrow, 14) = "N/A"
                            dataset(Lrow, 15) = "N/A"
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 10)
                        ElseIf dataset(Lrow, 14) <> "" And dataset(Lrow, 15) = "" Then
                            dataset(Lrow, 15) = "N/A"
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 13)
                        ElseIf dataset(Lrow, 15) <> "" And dataset(Lrow, 16) = "" Then
                            dataset(Lrow, 16) = "N/A"
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 13)
                        ElseIf dataset(Lrow, 16) <> "" And dataset(Lrow, 17) = "" Then
                            dataset(Lrow, 17) = "N/A"
                            dataset(Lrow, 18) = dataset(Lrow, 13)
                        ElseIf dataset(Lrow, 17) <> "" And dataset(Lrow, 18) = "" Then
                            dataset(Lrow, 18) = dataset(Lrow, 13)
                        End If
                End If
            End If
        Next Lrow
        .Range(.Cells(Firstrow, "A"), .Cells(LastRow, "T")).Value = dataset
    End With

    Application.ScreenUpdating = True

End Sub