[CeFurkan]

When you defeat a gym leader you get tremendous rewards and a badge

While you have that badge, you can not battle with that gym leader again to get those rewards again. Normally you can defeat NPC trainers daily. But gym leaders can not be defeated as long as you have that gym's badge

So you can reset your badges to battle with gym leaders again to get those tremendous EXP, Gold and Item rewards again

Badges can be reset from control panel > https://www.pokemonpets.com/Settings.aspx

And also can be reset from reward shop > https://www.pokemonpets.com/RewardShop.aspx