Was civilization (atleast architecture) gifted to us human in a terribly short period of time?
"Why" is indeed the relevant question. While Göbekli Tepe certainly isn't the oldest of sites to show human activity, I would agree it is the oldest to show monumental effort for the sake of religion—whatever "religion" may have meant to the people who erected the site. We simply don't know. Right now Göbekli Tepe presents more questions than answers.
But the stone structures we see there certainly didn't go up over night. I believe the monuments we see there today are dated to the tenth millennium BCE, but I recall recently reading where archaeological evidence suggests activity at the site occurred well before then. In other words, Göbekli Tepe was a site a long time in the making. Who knows what might have been there before the current monuments? What "on-the-job training" did its people experience, in the crafting of stone monuments over long periods of time?
As to how they figured out how to carve the monuments, I don't think that's terribly mysterious. The people of that region would've been well familiar with stone-working in their day-to-day Neolithic lives. Granted, it would've been in the form of tools and projectile points, but that would've been the start of it. The monuments themselves are only limestone, as I recall, and limestone is easy to work with simple tools—be they copper or stone.
The carving of the monuments is not remarkable in and of itself. They are fairly crudely carved. Much more impressive is how and why groups of hunter-gatherers banded together, marshaled their resources, and worked together well enough to achieve what we see there. Clearly it was a site of great ritual importance to them. Sadly they lacked any form of writing and could not leave us any tangible understanding of their belief system, so we will never be able to fill in all of the blanks.
Hm, perhaps Göbekli Tepe is all that remains of Atlantis. Oh my, I shouldn't say such things. Now all of the Atlantis nuts are going to creep in.