How can I fix a css conflict between my theme and bbPress plugin?

Hi. I am building a website that is live on http://www.redireito.com.br .

The theme is Deck, from MightThemes (bought at theme forest). I've installed the bbPress forum plugin, but I've got this: http://www.redireito.com.br/foruns

There is clearly a css conflict, but I don't have any skill to solve it.

Could you help?

Thanks