I think if ' I see' is refer to expression of understanding it's quite to 'Ach so'. And 'How are you' can be ,' Wie geht's?', ' Wie geht es?', or 'Wie geht es dir?'

ich sehe, wie gehts

I see = Ich verstehe oder Ach so. How are you? = Wie geht's? Wie geht es dir?

If you mean 'I see' as in like 'Oh, okay, I get it' then it is as Fatiya says: 'Ach so' If you really mean that you're seeing something: Ich sehe. 'How are you' Normally: Wie geht es?''or 'Wie geht es dir?' And 'How are you' Formal: Wie geht es Ihnen?

You need to be more specific. There are quite a few ways to interpret "I see" in German. Haw are you? = Wie geht es?