How can I convince my dad to get me a German Shepherd puppy?

Grr. I really want one, my mom said that those are heer favorite =dogs and that theyre beautiful, and thats coming from her! she is not a huge dog fan. we have a cat so thats why hes mainly saying no and he said they bark loudly and wuld you really pick of their poop, etc. I heard if i get it as a puppy and since my cat is only 1 that they can get along, plus i was thinking about having it outside in the backyard and basement, omg i want one so much. I told her, theyre good guard dogs, what if someone tries to kill me! but yeah that didnt work, then i said why do you hate me *fake cry* he said no when we go back to europe, yeah i live in america but i was born in europe ive been living her since i was 3 so yeah do the math. How can I persuade him? :DD I want to get a male puppy GS and name it like something mean, Judge or Rex or maybe Storm, not something cuddly. ;p