To get enough exercise, your puppy must have more space to play. He may be quite mischievous, too, or not completely housebroken, so he can't be given the freedom of the house. Put a tension-bar gate (designed for small children and dogs) in the entrance of the room you want him to stay in. At this age of 3-5 months, weather permitting, dogs of big or heavier-coated breeds can spend some of their time in an outdoor enclosure. They can be fenced in a puppy exercise pen or baby playpen. You can purchase a puppy exercise pen from most pet-supply dealers, or you can build one.
Four wired frames can be screwed jointly and bolted to a wooden platform using casters or wheels. If the height of the pen is one inch or two less than the width of the house doors, it can be transported from one room to another, or outdoors. While covering the frames, nail the wire on the outside. It's safer for the puppy because he won't scratch himself.
Since you may wish to enclose the puppy in the pen for a couple of hours, it is wise to add up a bed in which he could curl up for a nap. For most puppies, a wooden box would do nicely. Cut an opening in the side to serve as an entry. Hinge the top for a cover that can be put up for cleaning or left open if the weather is really warm. Put a blanket or other bedding inside and you have made a snug little harbor free from draft and chill. Sometimes a pup will refuse bedding of any kind and claw it out of his basket, box, or kennel. Don't concern yourself about it. If he favors a bare bed, there is nothing you could do about it.
Put the pen in the sun when it's cool, and in the shade when it's hot. Face one long side and one short side using canvas as a windshield. The outdoor yard for bigger breeds must have some shade as well as sun, and a place secure from drafts or wind, like a doghouse. If you leave the house, even for a short time, take your dog inside. Don't leave him alone in an outdoor enclosure when nobody is at home, even if your yard is fenced.