Fk them up early game, you win almost every one v one, don't be scared if you're low because you Olaf your passive and W will keep you alive for most of the time.

As long as the enemy isn't crazily fed, you will win almost every team fight and One V One, at this point, try to avoid being focused and try to fk them up as hard as you can then they don't get way too fed late game.

You still win every one v one, try to push as hard as you can to distract enemy, once you're low, hit minions twice and you are full health. Try not to 1v5 since Olaf is an early game champ, just push and kill enemy backlines during a team fight.