German Shepherds are such beautiful and smart canines. They make great family pets and work dogs. The average German Shepherd will typically grow for up to 2 years. (http://www.mygermanshepherdpuppy.com/)
The bodies of these dogs tend to grow much faster than their muscular system, so don't be surprised to see your dog gaining a bit of weight and looking more muscular while their overall body appearance seems to have stopped growing. It's perfectly normal.
German Shepherds are done growing physically and mentally after the age of 2-3 years
Large dogs generally grow in height until about a year then start to fill out, reaching full size around 2-2.5 years. They generally grow very quickly up until about 6 months when upward growth slows down.