For this achievement you can race against AIAs this one requires you to complete 5 circuit races in an online game, the fastest method is to do 1 lap race on
Camino Viejo De Montserrat - Mini Circuit against AI.
To create a game:
-Community
-Race Online
-Create Race
-Game setup
-Game Type - Circuit Race
-Environment - Camino Viejo
-Track - Camino Viejo Mini
-Max Players - 2
-Max AI Players - 1
-Laps 1
-Car Class - Any
Then select your car the
2010 Porsche 911 Sport Classic and change the AI car to something slow.
Start the race and complete 5 times for the achievement.
Here's a video, you do not have to own the car.