The way that you phrased that one question, which was passed on from your Christian friend, is an example of where theistic thinking tends to fail. They tend to ask the wrong sorts of questions ... or they fail to ask a properly basic question. Just like with the one you had in your discussion, they'll ask about the one true faith, rather than questioning the very usefulness of faith as a concept.
They'll load up a question with unjustified premises. Instead of asking, "So, how do you think the world came about?" they'll ask, "So, if God (by which they mean only their god, of course) didn't create the world, then who did?"
First off, who says that it has to be a who? Then, there's the loading of the word created, which forces in intention and will, which is a completely unjustified assumption.
Hell, most of the time, they probably don't even realize they're doing it. If they only talk about this sort of thing with fellow believers, they might have never even had their assumed premises challenged.
Like I pointed out in the discussion comment-section itself, lots of people probably assume that once your heart stops, you're completely, absolutely dead. That's just not true. Unless you get caught in the fireball of a nuclear weapon or catch a high-caliber, sniper-rifle round through the brain, brain-death is a long, gradual process.
There are LOTS of groups and forums to explore here. I particularly recommend the active, relaxed, freewheeling Hang With Friends. Canadian Atheists on Nexus would be worth "waking up" too. Groups don't clutter up a "timeline" or "news feed" page; some of us are members of many dozens.
And I keep discovering things through the "Latest Activity" in the lower right of each page. (Mobile view: menu, Activity.)
Greets, Halil, and welcome to Atheist Nexus! If you have questions, we may NOT have all the answers, but we DO have directions we can aim you in and suggestions to make. The point is to help you find your own answers, which I suspect many of us think is the optimum solution.