He's a cutie! I'd get him in puppy kindergarten ASAP! Mental exercise will wear an intelligent dog out much faster than physical exercise. Boxers (used to have them) are much like these dogs - super intelligent and easily bored; almost impossible to wear out, physically. Training sessions should be short (10 minutes) while young, especially for an intelligent breed, to avoid boredom, resulting in refusal to comply.
Is he food driven? Play hide and seek games. Hide pieces of kibble (only one piece per hiding place) around the house. Start out easy (a piece by a chair where he can see it), progressing up to pieces hidden in hard to find places. Teach the "find it" command. At first, lead him to the "prize", saying "find it". He's so smart, it shouldn't take too long for him to catch on. Obviously, don't let him see you hiding the pieces of kibble (kennel him or have DH take him outside while you hide the treats). Remember to take out the amount of kibble used at meal time for such games to avoid your dog gaining too much weight.
You can also hide yourself in increasingly hard places (DH needs to help you hold him while you hide), and let him find you. You can say, "find me". This is also good for having the dog always be aware of where you are and is helpful if he gets loose and you want him to come to you. Making it a game comes in handy when this happens.
Another option is to get some dog puzzles that have kibble put in them. The dog has to figure out how to get the kibble out. These puzzles come in varying levels of difficulty. This could be a way of feeding your dog and mentally exercising him at the same time.
