Tips on getting a dog not to pull as much?

Hello! I’m a relatively new sitter, I only have about a dozen bookings under my belt. I am currently doing hour long drop ins/ walks 3x a day for the next 3 days for an male Old English Bulldog who is about 5 years old. Today was the first full day of walks and drop ins and it was r o u g h. This dog is very untrained when not with his owner.

I’m a fairly strong and large person and I’m fairly difficult to knock over but he nearly knocked me over today when entering the house and just about dragged me for the first half of our walk until he got tired. I asked the owner for advice but was just met with he never pulls that strong, he’s just excited. So not super helpful.

He is really food motivated but taking treats with me didn’t work, I couldn’t break his focus on smelling things and walking. He has a Halti Front Control Harness which seemed to make no difference, I put it on how the owner showed me and double checked it was on right by checking online videos. Any tips or tricks would be greatly appreciated! I want to finish out this booking on a positive note if possible and then maybe never book with this owner again 😅Thank you!!!