u/First-Muscle-5997

So this is more of a rant post unfortunately but I posted about a week or so ago about kez. Everyone was so helpful and we took what they said into our training and it was amazing, we got to a point where he would see a dog and check in (most of the time, not perfect) . No lunging or barking which was amazing!! We even managed to walk past another dog that was very close (no way to avoid) and even spoke to the owner of the other dog with no reaction from kez. We are going on holiday in September and a friend has offered to have him for the week, I told her everything we do with his training and she’s been on walks with us so I can show her how we manage with other dogs. He’s met her before with no issues but I suggested she have him for a couple hours so kez can get used to her without me being there. She came and picked him up and i went through everything again, she’s walked him to her house which is only 5/10 minute away and she’s said that he was very reactive and pulled, barked at 3 others dogs. I asked if she followed what I said which she kept avoiding the question so I’m assuming not. I get that sometime he could have bad days but I we took him for a walk the next day and it’s like the first day we ever took him out, extremely reactive to every dog like he’d not had any training at all.
Even dogs that were normally far enough away where his threshold has been for the last 3 months he was still reacting which in extremely frustrating. I just don’t get why she wouldn’t follow what we have been doing and it feels like we’re back at step one again, I’m hoping over time we can get him back to a better stage. Sorry I know it’s a long post but I needed to vent somewhere 😂

So I’m looking for any advice with my 8 year old Staffy Kez . He’s amazing with people and kids. We got him 4 months ago and he is reactive to other dogs on walks and will bark and lunge, but he has improved a lot over the last few months with some training and getting his attention back to me before we reach the trigger. As long as they are at a good distance he can stay calm, it’s just when they get to close got him
He’s knows all the basics like sit,paw, lay down and he has just started doing these on walks (which he didn’t do before). He is very happy learning new tricks and he can learn them  relatively quickly.
I’ve watched a lot of videos and researched on what to but just don’t know if a trainer would be better. I also don’t know if he just doesn’t know how to “play” with another dog, from what we’ve seen his last owners had a “big enough” garden that they just didn’t taking him out the house at all. So he’s had a massive last of socialisation.
He has been out on 3 walks with other dogs with enough space in between, at first he barks and heckles go up but after a couple minutes he can leave them and carry on walking, which makes me think it’s more of he doesn’t know how to act? We have also bought him a muzzle just for safety since we’ve have a lot of off lead dogs approach us.
Just wondering if anyone has any tips or suggestions of what else we can do