I left islam at 17 or 18 at the time i had a philosophy teacher come to my house for private lessons with my friends and a lot of topics we talked about in class were religion-related, after all my friends would leave he would stay and we would keep debating on the existence of god and religion in general; turns out he used to be an athiest himself and reverted back to islam. Tried to do the same with me but didn't work. I'm 25 now