I agree not to use force as Streetcar mentioned. But it sounds like you're not. It sounds like you have a problem with him pulling. This is a very young puppy and he'll get it in time. It is not too young to start teaching him. Babies are sponges. But remember he is a very young baby and a little bit will go a long way. I also think a harness is best. Their little tracheas are very prone to injury from collars and definitely not a choke type collar. Just a soft harness is fine. Contrary to what some say, I do not think harnesses encourage pulling and I can demonstrate that with a video of my dog if requested. It is only possible for a dog to pull if he is being rewarded for pulling. (even if inadvertent)
I usually start puppies out in a safe place, like in your house or a fenced yard. I start out with no collar, harness or leash. I just encourage puppy to come along with me, turn with me, trot a little by my side, walk slower, zig zag and have fun with it. As he stays pretty close to you, feed teensy weensy, tiny tid bits of a tasty treat...reinforce FREQUENTLY as he's close to you. If he goes out ahead, turn and run the other way making squeaky, silly noises. Make everything into a game and you'll have him sticking close in no time. Use a squeaky toy and use that for a fun reward too sometimes. But a soft, tiny treat can be furnished quickly as you're walking along and you don't fall out of step. But at the end of a little session, let him know that his paying attention earned him a super cool time with you. I love how my dogs LOVE working with me as they get older. They are all ears when it comes to learning. They try so hard. They have a history of no pain, no serious stern stuff, no show-em who's boss...just fun learning new things.
After you've gotten him to LOVE trotting along close to you and turning with you, stopping here and there for some praise, put a harness on him...just a comfortable little harness. (I like Puppia brand comfort harnesses) Put a leash on him and do just like you did when he had no harness or leash on him.
When you advance to going on real walks, with more distractions, try to keep the distractions at a minimum and only do very short walks...just part way up your road and back for instance. Do just like you did before and when he gets near the end of the leash, pat your thigh and encourage him to turn with you and go the other way, remembering to treat often for his compliance. Keep the leash the same length so he knows when he's coming to the end. Never allow any tension in the leash to keep the walk going. He must learn that it doesn't work to pull on the leash. He likes to go, he likes to walk or trot. That is his motivation. Now, just prevent that if he pulls. It must happen every single time that you show him the pulling doesn't work to walk. Stop and wait for him to give you slack. Or take frequent turns. Turn and go back and re-trace your steps on the same, boring path he just took. Try not to wait for him to mess up. Turn frequently to prevent it, and Reinforce, reinforce, reinforce every couple steps that he does it right. (reinforce means reward that he LOVES) And it must alter behavior or it's not a reinforcer.
Apart from that, start working on teaching him eye contact. You can eventually ask him to watch you to get his attention on you better. It's a fun game you can do sitting on your kitchen floor. You hold some kibble or treats in both hands and make a closed fist. Hold your hands out to your sides a little bit. He'll grope, maul, lick, nibble on your hands but you do not open them. You wait patiently. He will eventually stop and look at you to see what's up. At that very second you click (if you're using a clicker) or use a word, like, "yessssss!" and give him a treat. Mark that behavior of looking at you. Do not give a cue yet. Get the behavior going, then when he's made the connection, add a cue at the same time, "watch." Or whatever you want. Gradually you'll add duration before he gets a click (mark) and treat. Later you'll be able to get his attention on you when needed.
He's a tiny, young baby. These training things are a process. It won't happen over night and you want him to love working with you. So make it fun, short little sessions...just 5 minutes at a time before you do something else and end on a successful note...something he does well and gets lots of attention for. Quit working with him while he's still loving what he's doing so he looks forward to the next time. Don't wait for him to get tired, bored or too distracted. Leave him wanting more.
Look for Kiko pup videos. She wonderful and has all kinds of videos for teaching things like focus, eye contact, walking nicely on a loose leash, a good sit and lots more.
I absolutely 2nd Streetcar's advice to read Culture Clash. It's excellent and a must read to understand some important things about dog behavior.
Good luck. Enjoy your puppy. And like Streetcar said, don't over do it. It sounds like you're doing just great.