So why is it your God? How are you so certain it's Yahweh? Why couldn't it be Odin, Ville & Ve, who then slay Ymir to craft the world from his corpse?
Interestingly, neither Hebrew nor Norse creation myths feature
creatio ex nihilo, which isn't really something you find in ancient creation myths in any culture. In the Norse myth the cosmos is formed from the corpse of Ymir, much as in the Babylonian creation myth it's formed from the corpse of Tiamat. The Hebrew creation myth from
Genesis 1 has things created from the Deep, which is an impersonal version of Tiamat, and which preexists the creation of the world. That's actually very typical for Middle-Eastern cultures and exactly what one would expect. But because nobody seems to study other Middle-Eastern creation myths, most don't realize what the Deep is supposed to represent, and they miss the fact that it's not created but preexistent.
The fact is that nowhere in the Bible is Yahweh shown to create anything out of nothing.
Creatio ex nihilo is a thoroughly modern concept; ancient people seem to have found it unintuitive, so they didn't construct their myths that way. Even in the creation myth of
Genesis 2 we see that everything is made of something that already exists (Adam from dirt, Eve from Adam, etc.).