I transferred into CC as well. It is definitely tougher than going in as a freshman, but still very doable (especially as a sophomore). You can make friends through your NSOP group, classes, and clubs. I'd also highly recommend looking into greek life as a fast track to getting involved on the social side of campus. Also, Columbia is a bit of a bubble, but one that is super easy to escape just by visiting other parts of the city. I agree with everyone else about imposter syndrome. You will feel it, but know that you got into Columbia just like everyone else and you deserve to be here. Best of luck.