For Christianity, as any other religion, their is no possible way to prove that god doesn't exist. We go by facts and evidence that lead us to conclude that his existence is very unlikely. I or anybody else could create a new religion like Scientology for example, and claim we have a new god. There is no way you could solidly make it a fact and prove this new god doesn't exist, but you can use logic as a way of saying it is nearly impossible.
When its it convenient for theists they "understand" gods creation and when its not they "cant". Religious people all say that they know what and who created the universe but we cant possibly know whether or not what is going on is right? Thats pretty stupid. To know whether or not the universe was created you would have to understand some of it. To know whether or not what happens here is right you have to understand some of it. So why is it that you can understand some of it and we cant? I know if a being of some sort did this then they are wrong no matter who they are because it is wrong to hurt innocent people no matter who you are because who you are doesnt determine what they deserve. People should be treated as they deserve to be treated and there is no other way of gathering an idea of what people deserve. If you know whats right and wrong then you know whether or not people deserve a reward or punishment and which reward or punishment they deserve. Its not hard to see that hurting innocent people makes you deserving of harm whether your god or anybody. What makes an act right or wrong is its congruence with what the recipient deserves. What i do should be judged the same way no matter my superiority as my superiority doesnt determine or even effect someone deserves. People deserve to be treated the same way by people as they deserve to be treated by god.