are 「なんとかなる」 and 「だいじょうぶ」the same?
sorry if someone already asked it, but i couldn't find.
"なんとか" means "somehow" so "なんとかなる" literally means "it will become (good) somehow". When you use "なんとかなる", you are not 100% sure about whether you will be okay or not. There is a hint that you are somehow relying on the nature to take its course; "Que sera, sera"; whatever will be, will be. Adding "か？", "よ" or "さ" just changes the statement into a question, an exclamation, an advice or the like; it does not change the level of your confidence in the statement much.
"大丈夫" on the other hand is a strong affirmation that everything is okay. Although it is a set-phrase, we can see how strong an affirmation it is from the literal meaning of its components - 大 means "big" while 丈夫 means "strong and durable". It is no where as wishy-washy as "なんとか". When you use "大丈夫", you mean it.
However, it's worth nothing that both of them sometimes are used together in the form of "大丈夫だよ。なんとかなる。". Rather than looking at it as self-contracting, I would say that it is a pattern of conversation, where you give your assurance first and then give a hint to the other person that you might not want to take the full responsibility of whether he will really be okay or not later, for when you don't want to say "It's okay, I myself will make sure you will be okay".