I'm new here too but not to dogs. I have an Aussie that is an extremely high drive dog however I've had GSDs that were the same but much larger. I don't mean excitable, I mean driven to work non stop, full throttle all day if necessary.
I train a "sniff " command for potty stops and just checking things out. When it's time to heel close then I command that. What ever commands you use.
My dog can easily pull a lot more than her 60 pounds if she she has traction. So the free sniff can be a bit of struggle especially if a walk entails 3-4 miles. Over a period of time I have had her do close order heel the entire walk. Other times she is Free to sniff except for danger areas, streets, crossing paths or anything else that requires her to be close to me.
She is trained to come to heel on command or sniff on command. We do this every day multiple times and multiple locations.
One thing I do is slip the handle of the leash on my left wrist as a " choke" on my wrist and use a left hand glove. It's nearly impossible to drop the leash accidentally this way. Then as the dog sniffs I use my right hand to get a half wrap of the leash anytime the dog gives slack. As she moves away I can slow the leash like a capstan with my right hand. It puts drag on the dog. Essentially tight leash. The purpose is to exercise the dog and prevent leash jerks. I even do this in the field with a 30 and 60 foot leash. I'm constantly coiling these up.....not talking on the phone or listening to music. It's a full time effort on my part. I get good exercise too resisting pulling. When I get tired (not if..) I just command " heel" (what ever command you use ) then we walk close for a while. This is where we practice other commands. Front, heel on the right side, heel leading, heel following. Walk in figure eight, serpentine (alternating left and right half turns) about turns. Stops with sit stand or downs. Food avoiding, leave it, and any thing else I can dream up. There is a large rock that we rest on sometimes. Just use your imagination. I mix training with walks as these are necessary As a bored Aussie is a destruction machine with an unmatched imagination for getting into things.
I don't do a lot of correcting, rather redirection. Pulling to the end of the leash, I do something like this :,hey, Sam look at this and point to something in the grass 180 from the current direction. I've already dropped a small hot dog treat. When she finds it I praise. To start I'll also give another treat. If she resumes the pull I do it again maybe with two treats. It didn't take long to get to " hey Sam" and she would stop pulling and come running. I rewarded heavily again. At first anytime she hung around me I gave treats. Liver is her extreme value treat so walks sometimes used a quarter pound of liver. I do lots of short recalls on leash during walks.
It's a bit complicated exercise and it takes some patience and thought on your part. I like to think the dog wants to be near you because that's where the tasty treats are. My goal is the slightest indication by me that a treat is in my hand is time to come to me. You can put a lot of drag on the dog to tire him out some. I have better training on the way home rather than on the way out as the dog is a bit tired. Eventually you can back off on treats and do just praise.
The bottom line is I don't like force on this as it's easy for this to become avoidance of you and recalls can become more difficult.