German sheppard and boxer mix?

alright my sister has been begging to get a dog. my mom likes dogs and my dad relented and she got a german sheppard boxer mix. as i suspected she played with him for a week and got bored with him. my mom and dad dont really want anything to do with him and i am the only person who remembers to feed and water him. as such im also making it my responsibilty to train him. does anybody know much about how to train a mix like this? i dont have much experience with dogs but he seems like a smart dog and i dont mind spending a half hour or so a day trying to teach him. any help or pointers is greatly appreciated!