My Dog Hobbit

So, none of you guys know this but I have to dogs named hobbit. He is a yorkie. To me  he’s so cute! But I need some help. When Hobbit sees a cat or dog besides other dog (Moti). He goes CRAZY :(. I try to calm him down but he just goes at it with the cat or dog. I even put my finger to his side but he doesn’t care. My dad tells me I need to train him and I do but he’s hopeless. He just stares at me :). It’s very cute I have to say. But I don’t know what to do I need Advice:)?!