Standard dump cake portions:

2 15 oz cans fruit or pie filling(peaches in syrup is the most popular).
1 pkg cake mix (yellow is the most popular)
1 20 oz bottle soda pop (lemon lime soda is the most popular)

It looks like you used twice the amount of fruit and twice the amount of soda for the amount of cake mix. Ideally, when finished the top of your dump cake should be golden brown and a little crusty, the center should be cakey, and the bottom should be like a thick cobbler.

Also, it sounds like your biscuit mix was far too wet as well. That will take a lot longer for the biscuits to firm up and brown than normal cooking time.