How do you say "What's up" or "How are you doing" in Spanish? (in a natural way)

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"What's up?" is in spanish is "¿Qué pasa?" and "How are you doing?" is "¿Qué estás haciendo?"

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que mas, como andas?, que onda? , como te va? well this what i most remember now

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Ademas uso "que tal?" y "Como estas?"

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What´s up? = (formal way) Que pasa?!! = (informal way) Que pasa tio!!!?
How are you doing?= (formal way)Que estás haciendo?= (informal way) Que haces tio!!?

more or less :p

I Hope that I helped you :)