How come? and What for?

Hello! Maybe anyone know it. Can I use instead of ‘why?’ ‘how come?’
and ‘what for?’
Thank you for your answer.
Terminator :evil:

Hi Terminator,

You can use these both for ‘why’ - but ‘how come’ is used in conversation. Remember the construction:

Why are you doing that?
What are you doing that for?
How come you’re doing that?