Arguments against Christianity via Science

Yeah, I have been not liking religion for a long time, but recently I befriended a highly religious Christian friend that was open to discussion

The problem is: I seem to think that whatever I try to refute him with is wrong, and my own experience with science and the natural study of everything is too small to make an accurate refrence as to how Christianity is disproved

I brought in some bullshit about evolution and biology, but I failed horribly

So give me some proof that is irrefutable or otherwise widely used

I know there was another thread like this, but it didn't specifically address the question

To believe in an afterlife you have to believe that an invisible part of your body goes to a magical place after you decompose. It doesn't take a genius to realize this is totally mental.