ब्राह्मण वेश में कौन था? उसने प्रतियोगिता किस प्रकार जीती?

Sorry, I can't translate this.

In that time, there were only two warriors who could win the competition, they were Arjun and Karn.

Draupadi knew about it and she wants to marry Arjun and not Karn. Because Karn was devoted to Duryodhan, and according to Mahabharat Duryodhan was a bad man.But she could not make such an excuse. That's why she rejects him by saying that he is a Sut Putra (Sut is a class of people that was considered to be a low class of people).

And the second option was left for Arjun, and it was Arjun in the disguise of Brahmin who won the competition by penetrating the fish's eye as it was the only condition for the competition. He was disguised because his mother, Kunti did not want anyone to know that he was Arjun.