if you are putting in the effort and not seeing the results you want then it is something you are doing wrong. if you dont see improvements then yeah a trainer would be a good idea. or you can try new ideas yourself because what you are doing right now isnt up to your standards.
constantly correcting the dog isnt going to help if he isnt crystal clear what you are wanting. you need to train him to understand. youtube michael ellis leash pressure. thats a good place to start.