How do I stop my dog from laying down all the time during a walk?

A good boot to the patoot usually works.

the dog whisperer.......

Stop everytime he wants to walk and sit down.

Teach him the 'heel', which means SHORTEN THE LEASH, he needs to have his shoulder no more than 6" away from your left knee. You hold the leash in your right hand and your left holds the section of the leash a foot away from his collar. You don't let him lag behind, go off to the side or surge ahead. Stick with a brisk walk. Talk to encourage him.

Stop letting him do the leading. You're the owner, you're the one training him in what a walk is supposed to be. If he wants to lay in the grass or on the ground to smell everything without moving, that's when you take him to a dog park to do that to his heart's content. But a 'walk' is a 'walk'.

He lays down for 10-15 minutes for each 5 minutes of walking, because YOU LET HIM.

Get him to a VET. He could have an issue with his hips that's making it painful to walk.

I do hope you bought this dog from a registered, reputable AKC show breeder and not some backyard breeder on craiglist? Good breeders only breed dogs whose hips have been tested. You could have bought an ill bred puppy with bad hips and its already having issues.

"we're forced to just stand there until he decides to stand up"

The dog thinks HE'S the boss. You need to keep the leash pulled short, so it will be uncomfortable when he tries to lay down. Basically, let the dog know YOU are the boss.

Just ask "the dog whisperer". It's exactly what HE says.

Assuming the vet says he is healthy, you state your own problem. "We make sure not to pull too hard on the leash so there's no discomfort." This is a big dog and it sounds like he's taking you for a walk, not the other way around. He doesn't understand what a little tug on the leash is. Get him on a body harness so you can pull as hard as you physically can without hurting him. You have to pull HARD as soon as you see him slowing down. There's plenty of humane ways to let him know your the boss without causing pain. He won't do this if you train him, it's just going to be a lot of almost dragging him down the street until he gets it.

I would first make sure that discomfort is ruled out as a possible cause. This breed is prone to hip dysplasia, elbow dysplasia, and luxating patellas, especially when not bred with appropriate orthopedic screenings. This doesn't strike me as normal behavior in an adolescent dog that should be pretty active and eager to go places.

If the vet gives him the all-clear, pick up the pace to a brisker walk and don't allow him to dawdle long enough to lie down.

Start jogging instead of walking. Get a bike, skateboard, jog, run....pick up the pace. Put him through some of his obedience training. If he is not trained in Basic Obedience then you need to get him trained. You can learn how to train him online. Tons & tons & tons of information & instruction on any kind of dog training, even the 7 basic commands that are taught in Basic Obedience. If you are going to walk a dog I think you need to have 100% control of the dog & that is what Obedience Training teaches the dog. Basic Obedience is obligatory. He does it right or he gets a correction.