There are still two rules that I'm not sure I understand correctly.
Raffles' instructions allow a player to move 5 extra steps. I understand that I count those steps beginning from the moment I use the building. For example, if I am two fields away from the Raffles' instructions, do I move two fields, use the building and finally move 5 further fields?
You just gain 5 extra steps, so in your case, you have 6 steps left (5+1) after picking up the 5 extra steps. Note that you can split those steps between your two pawns (if you already have the second one in play).
The second thing is starting from 0. Does it mean that players lose all of their points when they exceed the limit of 60?
No no, you just keep counting. But note that the "flags" don't generate income any more if you're past the 60.