I'd like to correct your mistakes before answering your question. 1.ーげんき！ 　ーげんき？ 　　　↓ 　ーげんき？ 　ーげんき！ 2.wile 　　↓ 　while Answer:We use "げんき？／おげんきですか？" when we met someone whom we haven't seen for a long time. The "げんき？／おげんきですか？" is a translation of "How are you?". It's right as a translation. But customs of greeting are different. I don't understand "おやすな". Is it a mistake of "おやすみ"?

Hello, im mexican and i'm learning japanese as well. In my experience, learning this language you have to understand their culture because is complete opposite to our culture. so the important part of japanese is formality, knowing how you have to direct your words to someone and understand that because of the difference of cultures we can not translate directly the things as we would say in our countries, but we have to found the way we can express ourselves in their way. And that's interesting, you're about to learn a lot of interesting things and the beauty of a different culture. Yes the expression that you used at first is a good translation but is disrespectful to use it with some one you barely know. The best you can do is try to learn the formal ways of japanese, once you have a lot of friends and they tell you that you can speak to them with informality then they will teach you how to do it. 頑張ってくださいね! Greetings!