1. A whole new ball game: a situation that is very different from the one you are used to. [Longman]
''I used to be a teacher, so working in an office is a whole new ball game.''
''Eu era professor, mas trabalhar em um escritório são outros quinhentos.''
2. Be another/a different kettle of fish: to be completely different from something or someone else that has been talked about. [Cambridge]
''Having knowledge is one thing but being able to communicate it to others is another kettle of fish.''
"Ter conhecimento é uma coisa, mas conseguir passar isso para as pessoas são outros quinhentos.''