Instructions
Obtain a fighting Pokemon if you do not have one. If you chose Torchic as your starter Pokemon, it gains the fighting type when it evolves into Combusken. Rock Pokemon, like Nosepass and Geodude, are also useful when fighting Norman's team.
Train your Pokemon team until they pass level 30. Norman's strongest Pokemon is a level 31 Slaking, so your team needs to be around that level to win this fight.
Attack Norman's two Slakings with fighting or rock moves when he sends them out. Slakings have the Truant ability, which means they attack you every other turn; however, their attacks are doubly powerful. Do not attack any of Norman's Pokemon with a paralyzing, poison or burning move; these attacks increase your opponent's attack power.
Heal your Pokemon with Super Potions if they take too much damage from one of the Slaking's attacks. Use a Revive potion to pick up an unconscious Pokemon, if necessary.
Take out Norman's Vigoroth with fighting attacks in the same way you defeated the Slakings. You are victorious in the fight against Norman after all three Pokemon have been defeated.