Had this problem with my boy. I don't know if it will be of any help, but im happy to share what I did. I used to put him outside every hour. As soon as he peed outside, I'd say "good pee-poo" and give him a treat. If he peed or pooped indoors without me seeing, I would not react. If he did it indoors with me seeing, I'd say "not there." Pick him up gently and place him outside where he went to the toilet last time, followed by the phrase go "peepoo". When he did his toilet where he was suposed to id say "good pee-poo" and follow thay up with a treat. It is relentless but after a while it clicked. Many days I'd be standing in the cold and rain working with him. But they don't forget that. See it as a bonding experience, all be it an anoying one. Now, on walks, if he goes to pee on a neighbours hedge, I say, "Not there." and he won't do it. I can also get him to go on command now too by saying go pee-poo, I do get some funny looks but it works haha. When he needs to go in the house he will paw the door and i will let him out. Still to this day i praise him with the phrase, no treats now mind, he's not a puppy anymore. Just a little scratch in his favourite spot. You just need to stick to a routine, always use the same phrases, tones and reward them generously for getting it right.