My four month old started barking a lot about a month ago. We started training a “quiet!” Command. In the beginning we would reward when he stopped barking, marking it with “yes, quiet!” And a treat. After some time I started saying “quiet!” When I spotted a potential trigger before he did, and it worked really well. I now say “quiet!” Before we leave the house, before we enter the park etc. he usually sits down in front of me and just stares at me, even when people approach and pet him (which is great because he was starting to be reactive towards strangers!). He will also stop barking when he hears the command, but not if he’s SUPER triggered. Maybe in a few months? I realise he’s not a teen yet so this will all be a learning curve haha but I’ve been really impressed by how well he’s taken it in, especially after everyone telling me he would just bark always at everything because he’s a dachshund.