A: It would be so cool if I can win this contest. I don'tthink I'm good enough, though.

A: 要是我可以赢了这项比赛的话会有多好。但我不认为自己够好.

B: Give it a shot! You'll never know.

B: 试试看啊! 没试怎么会知道!

"cool" 是"很棒"的意思. "You'll never know." 是"你不知道会怎么样"的意思.

要想说, 我知道这个可能没戏.你可以说,I know it is a long shot, but Iwould still like to give it a try. 你起草了一份计划书,发给项目组里面的同事请他们帮忙修改,你可以说,this is my first shot at the project proposal, please feelfree to edit as you see fit. 你也可以说, this is my first stab.Stab是桶一刀子的意思, 放在这里就变成my first try.