Hi, I'd like to take the 3 Food packages, but I'm willing to negotiate on the Water and Firewood
Hello, understand and I can be flexible on the Food but in return I would like 3 Waters. 
OK I'm willing to let you have 3 waters, but I would like 2 of the remaining Firewood
That does sound reasonable, however I was wondering why you would need the excess fire wood. I dont think I brought enough from the store. 
Glad we're aligned! I don't have much either and was hoping to use for a proper fire, which is why I'm interested. 
I was also planning to start a proper fire with the wood, however I am not good at starting fire to begin with so I was wondering if I could have the extra
Would you be willing to give up 1 Water in exchange for getting 2 Firewood total?
That does sound reasonable but I really need the water. On the other hand, if you really want the firewood, Ill glad take one food for the excess. 
Let's just go with you getting 3 water and 2 firewood then. I will take 3 Food and 1 Firewood. Deal?
That sounds good to me