On Olympic Square Forward you are 3 main tips you have to know:
Use the sidewalks before start/finish to can gain a little bit of speed by jumping over it (see Sidewalk boost).
The first corner of the track is done with a normal DS with both Stab on and Stab off, and slightly brushing the wall with stab off only.
The corner at the trees can be a bit tricky, but no DS is needed.
Other then that try to keep a tight line through corners, while try to avoid most sidewalks
Reverse
For the start of the lap it is important to get enough speed out of the last corner. To do so try to approach the last corner from the left side, driving over sidewalk, and then use DS
Drive to take most corners tight, otherwise you will loose time
The corner after the tree section becomes a very small Micro DS Drift, since now you are entering with more speed then on OS.