Well I do not see the reasons why giving someone a tumor

Compare the two statements:

I don't believe in god, because my friend's young daughter got leukemia, and it's unfair for a child to get a serious illness.

I don't believe in cancer, because my friend's young daughter got leukemia, and it's unfair for a child to get a serious illness.

The second statement clearly makes no freakin' sense -- stuff doesn't exist or not exist because it's fair or unfair. At least, real stuff doesn't. Which is my point here, "god" isn't even a hypothetical thing, it's just a construct that has to do with how you feel about yourself and other people and the world in general.

And by the way, fair and unfair are narratives -- not real things. Diseases have to do with the mundane -- profane -- machinery of life, and people get sick the same way a car breaks down. That's not because the car "deserved it" but because something happened in the machinery.