This exercise is one of the hardest yet most effective ways of learning German. You will very likely fail bitterly for a while. I understand that that can feel frustrating which is why I suggest you see this as a positive challenge: any answer you get right or come close to is a win. See how many wins you can get. Even a single win is a huge success. You are allowed to use the little hints (i-buttons) which usually contain the English translation for the wanted word. It's also a beautiful opportunity to learn to deal with frustration as I can assure you that your failing here will only have positive consequences in the long run.