I want to buy a new dog, but I am afraid my 8yr old Rotweiler will get Jeaolus and attack it, what do u think?

my dog is the Jealous type, he does not care for food as much as me walking him or him chasing a cat/ he is going to turn 9yr soon. And I was hoping to buy a new dog so he can learn the tricks and obedience from my existing dog; I know he like calm dogs that he can boss, but if I bring him a puppy or small dog I am afraid that it might attack it especially that its entering his territory, what do you think? thanks