in what period of time did all of the sections of the wall join to make one great wall?

Jenny, you should understand that many dynasties rebuilt their walls. As time goes by, some sections were ruined. The most intact wall was built during the Ming Dynasty (1368-1644). Some sections were newly built and some others were restored based on previous walls. It starts from Jiayuguan Pass in the west and ends at Shanhaiguan Pass in the east. The Qing Dynasty seldom spent money building the wall.