Is this your first dog? Six months for dogs imho is the equivalent of 12 or 13 for kids. You have to give him things he can chew (is he teething?) and put those that he can't out of reach, indicate calmly that jumping up is not an option...teach him to sit when greeting people and praise and reward him for doing it and use barriers to stop him going where you don't want him. Just like teenagers, when dogs get to the difficult phase, you can't just wait for it to pass, you have to train through it. Give the dog as much mental stimulation and interraction as you can, as well as physical exercise, this will tire out his brain and make him settle better. I am a weimaraner owner, generally they don't get sense till about 2 years old, but there is lots that you can do while they are getting there. We channelled the excess energy of ours into hunting games around the house or garden and teaching them to find, by scent the exact pinecone or piece of log that we had thrown or hidden, we also taught them to track one of us hidden in the bushes, which is great fun, teaching the "find" command first by throwing then hiding a piece of cheese, then substituting an article and rewarding for the find and retrieve. Classes are a good idea but you MUST practice at home as well and make sure that its fun for all concerned. Our first dog learned that it was "funny" to steal a sock or shoe and then parade slowly past us daring us to chase him. He never harmed the item, although like all dogs, he chewed through the teething stage. He kept the joke up all his life even when he couldn't really run fast enough to get away from us and we had to run slowly so as not to catch him!