To defeat Barroth in Monster Hunter Stories, you need to study its behavior first. It often charges, so you should be good at dodging. When it's in the middle of a charge, it might expose its sides or belly. That's the perfect time to strike. Additionally, bring some items like potions to keep your health up during the battle.
First, you should understand that Barroth is a tough opponent in Monster Hunter Stories. It has a thick hide which can be difficult to penetrate. You can use a monster with abilities like breaking parts to make it easier. Try to stay mobile during the fight, don't let it corner you. A good strategy is to use ranged attacks when it's far away and then switch to melee when it gets closer and is in a vulnerable state. You also need to keep an eye on your stamina and not overexert yourself.