There are some folks who want to complete every quest as a personal objective, but I would suggest just skipping it. The quests in this game are very secondary, and most of the prizes are easily obtainable in other places.
I think the only other thing you can do is wait until you have increased your squad size in hopes you can win. Manual fighting may help, if you know how to take advantage of terrain. Check out all the fighting tips in that section of the Forum. I suppose you are both too low level to have gotten any troop enhancing buildings, such as Unleashed Unit Upgrade or Magnificent Mage Multiplier?
My last helpful tip, if you are going to try and fight, is to use five of the same troop rather than splitting it up 3/2 or 4/1. For some reason, five of the same tends to work better. Check all of your fights until you can find 5 that work best against one type that you have (I find avoiding mages to be helpful).
Sorry I couldn't offer better advice!