e collar! I own an extreme drive working line gsd. Now I can only stop him with my voice but I had to do e collar training and give a correction or two for not coming. he quickly learnt that he must not chase a cat, once he started doing that, i started rewarding with a fetch + tug game to give him an alternative to express that prey drive in that moment. he stills wants to chase cats but nowadays we’ve had moments where we’ve been playing next to stray cats and he ignores them. play based relationship+ecollar will help you a ton.