Based on the update, a loop is required, avoiding .Select will still help performance:

Sub test()

  On Error GoTo CleanExit
'  Application.ScreenUpdating = False
  Dim row As Long
  For row = 40 To 1539
    With Sheet1
      .Range("C2").FormulaR1C1 = "=R" & CStr(row) & "C2"
      .Range("C3").FormulaR1C1 = "=R" & CStr(row) & "C3"
      .Range.Cells.Item(4, row).Value2 = .Range("e2").Value2
    End With
  Next
  
CleanExit:
  Application.ScreenUpdating = True
  
End Sub

Note in this case the With Sheet1 - you can use the worksheet's (Name) property as a direct reference to it (you'll have to modify this for your Workbook):

Note that this is not the same as the .Name of the worksheet as displayed on the "tab":

Additionally, I've added Application.ScreenUpdating = False, but left it commented out for now. Make sure your new code is working properly before enabling this. This will prevent Excel from refreshing the screen with each step it takes. Removing all the UI activity reduces the amount of execution time (it's not a panacea, though). Note the addition of the On Error Goto... to ensure that if anything were to go wrong during execution, it will reenable ScreenUpdating. If you don't weird and confusing things happen.

As best I can tell, Sub CF_Amb_Pr_NG() sets cells C2 and C3 to formulas that changes with each iteration through the loop, then ends with them set to "=R1539C2".

You then copy cell E2 to each row in column D from 40 to 1539.

Unless there's something going on with the value in C2 and C3 that somehow impact E2, if you really want to stick with the .Select and .PasteSpecial this should do the trick:

Sub test()

  With ThisWorkbook.Worksheets("Sheet1")
    .Range("E2").Select
    Selection.Copy
    .Range("D40:D1539").PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
    .Range("C2").FormulaR1C1 = "=R1539C2"
    .Range("C3").FormulaR1C1 = "=R1539C3"
  End With

End Sub

Otherwise, I'd suggest this which is even easier:

Sub test()

  With ThisWorkbook.Worksheets("Sheet1")
    .Range("d40:d1539").Value2 = .Range("e2").Value
    .Range("C2").FormulaR1C1 = "=R1539C2"
    .Range("C3").FormulaR1C1 = "=R1539C3"
  End With

End Sub

It copies E2 to D40 through D1539, then it sets C2 and C3 to the final values they have in your loop.

Make a similar change to Sub CF_RH_NG().

If the value in E2 changes with the values as determined in C2 and C3 for each iteration through the loop, I'd strongly suggest that you add a helper column (out in column Z or LLL or someplace) that calculates E2 for the current row, then simply make the formula in D40 read =LLL40 (manually copy that formula down to D1539 one time), and be done with it - no need for code at all.

These simple assignments should execute in a second or two (Excel is notably slow in copying in my recent experience), but significantly less than the 10 minutes you're currently experiencing.

As best I can tell, Sub CF_Amb_Pr_NG() sets cells C2 and C3 to formulas that changes with each iteration through the loop, then ends with them set to "=R1539C2".

You then copy cell E2 to each row in column D from 40 to 1539.

Unless there's something going on with the value in C2 and C3 that somehow impact E2, if you really want to stick with the .Select and .PasteSpecial this should do the trick:

Sub test()

  With ThisWorkbook.Worksheets("Sheet1")
    .Range("E2").Select
    Selection.Copy
    .Range("D40:D1539").PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
    .Range("C2").FormulaR1C1 = "=R1539C2"
    .Range("C3").FormulaR1C1 = "=R1539C3"
  End With

End Sub

Otherwise, I'd suggest this which is even easier:

Sub test()

  With ThisWorkbook.Worksheets("Sheet1")
    .Range("d40:d1539").Value2 = .Range("e2").Value2
    .Range("C2").FormulaR1C1 = "=R1539C2"
    .Range("C3").FormulaR1C1 = "=R1539C3"
  End With

End Sub

It copies E2 to D40 through D1539, then it sets C2 and C3 to the final values they have in your loop.

Make a similar change to Sub CF_RH_NG().

If the value in E2 changes with the values as determined in C2 and C3 for each iteration through the loop, I'd strongly suggest that you add a helper column (out in column Z or LLL or someplace) that calculates E2 for the current row, then simply make the formula in D40 read =LLL40 (manually copy that formula down to D1539 one time), and be done with it - no need for code at all.

These simple assignments should execute in a second or two (Excel is notably slow in copying in my recent experience), but significantly less than the 10 minutes you're currently experiencing.