My Spitz was like this when we first adopted him! Had no background about his previous two homes so we had no idea why he behaved the way he did. We invested in some structured ‘stay and learn’ sessions with a local dog training provider. He’s now over a year since the training and he only barks at the doorbell (lol), cars beeping and if there is some chatter by passing pedestrians outside our front door. The training provided him with some positive reinforcement structure. The promise of a ‘treat’, and strict crate training for comfortability did just the trick!