Göbekli Tepe is the oldest megalithic site discovered anywhere as of now, dating to the Prepottery Neolithic A, and it is certainly a fantastic and very important place, but its interpretation is still very much up in the air. It is not the oldest site in general, just specifically the oldest evidence of megalithic construction (an important distinction). Schmidt, the main investigator from 1994 to 2014, had supposed the place was a communal "cathedral" which was constructed and maintained by a scattered population of infrequent visitors. That claim is now generally questioned. Still, there is no real evidence (to my mind) of any sort of permanent settlement at the site, and no evidence of agriculture. To call the place a settlement is pretty inaccurate at present, and it looks nothing like other, later Neolithic sites which were clearly permanent settlements, and nothing like earlier, epipaleolithic sites which offer evidence of human settlement.

So to answer your question: Göbekli Tepe has not, as of yet, told us anything about the transition to permanent settlement, or anything about the shift to agriculture. It raises interesting questions about megalithic building, and absolutely smashes our previous estimates for when such building began; and it raises larger questions about what humans in the region were getting up to, and why. I partially still agree with Schmidt that we should stick to the basics of what we know: humans were coming together there, whether from locally or from far afield; they were eating together there, and we know this because we have the many bones of their meals; and they felt it worthwhile to construct the place, for whatever function, through cooperation. To guess that it was related to "religion," or the observation of communal superstition, or some other similar reason, is a pretty good initial guess.