How to loop through massive data with fastest code

Hi,
I have this code to lookup some values. But number of rows of the data is over 30K, so it takes years to run.
can help to advice what is the correct code to use instead?
Besides, how to set password for the VBA code, so that users will not access to it?

Thank you.

Sub LookupV1()

    Sheets("Original").Select
    
    i = 2
    Do While Range("A" & i).Value <> ""
    
    If Range("A" & i).Value = "F11" Then
    Range("C" & i).Formula = _
    Application.Vlookup(Sheets("Original").Range("B" & i).Value, Sheets("Loc").Range("B:C"), 2, False)

    ElseIf Range("A" & i).Value = "D05" Then
    Range("C" & i).EntireRow.Delete

    Else
    Range("C" & i).Formula = _
    Application.Vlookup(Sheets("Original").Range("A" & i).Value, Sheets("Loc").Range("A:C"), 3, False)
       
    End If
    i = i + 1
    Loop
      
    
    End Sub