Why it happens
Dogs walk faster than we do and they are interested in things that are ahead of them. Pull, and the interesting thing gets closer. That is the whole mechanism, and it reinforces itself several hundred times on every walk.
It follows that the fix is not a stronger correction. It is making sure that forward progress only ever happens when the lead is slack.
Equipment buys you the chance to train
A front-clip harness does not teach anything by itself. What it does is stop a strong dog from towing you, which gives you the physical capacity to stand still, wait, and reward the moment the lead softens. For large and powerful breeds, that capacity is the difference between training and hanging on.
Avoid anything that works by causing pain or restricting the airway, particularly with flat-faced breeds. It suppresses the pulling without changing what the dog has learned, and it costs you trust you will want later.
The two-minute version
Start in the least interesting place you have — a hallway. Take a step. If the lead is slack, mark and pay at your leg. If it tightens, stop and wait, without pulling back, until the dog releases the pressure itself. Then move.
Two minutes of this at the start of a walk is worth more than thirty minutes of drifting. When the dog is reliable in the hallway, move to the driveway, then the quiet end of the street. Expect to lose ground when the environment gets harder; that is normal, not a setback.
This is general guidance, not veterinary advice. If your dog is showing fear, aggression, or a sudden change in behaviour, speak to your vet before starting a training plan.