You learned how to ride a bike a month and a half ago and you're already talking about going down stairs? I'm not gonna tell you you're wrong, but I will say that's pretty damn adventurous!
I'd suggest getting some more experience so you develop some feel for how different tire pressures work (and more importantly, how shifting your weight forwards and backwards works and other bike-control stuff like that) before trying that. But then again, I've been riding since I was a kid and I still shy away from stairs so what do I know?