[solved]Stuck on quest

Greetings, i'm stuck on a lvl45 quest.

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Got it from Eagle no Marin, I go to the waterfall and i find Leo no Aiolia, he give me another quest, a countdown start and i fight with Aiolia, even if I beat him he remains with 10hp and the countdown  continue. I continue to fail this quest.

Any hint?

Post screen of quest (i mean screen of the place where you fight him) and probably you need use your main clothes and hit the monster with special skill.

use the skill with a fist with a red background that is located in the second tab of skills pannel

Solved Thank You!