Como dizer "Por que me toma?" em inglês

Simon, I find myself astoundingly incapable of being sure of what you mean sometimes. Blame it on my rudimentary Portuguese. In any case, from the apparent context I'm going to guess it means "What do you take me for?"

Henry, you may find yourself incapable of being sure of what I mean, but it's just in theory, because you do very well. What you know about Portuguese I'd like to know about English.

If I understood it:

Por quem me toma?
(What do you take me for?)

Por que me toma?
(What's the purpose of all that?/what do you meant by asking that?
What's that for?)

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And yes, Simon, I am a (Brazilian) Portuguese speaker, with many friends and tons of books that I read in Portuguese. Not to mention my travel mileage and many friends of several regions in Brazil. Yet, with all that, I got puzzled with "você me toma", it got me thinking "from which region?" or is it Portuguese of Portugal, or with Spanish influence?
Anyway uncle Google helped me out and I learned a new expression.
Although, I couldn't place where it comes from (region, or time it was/is spoken etc). But, it's welcome just the same, I like to learn new words and expressions.

Esta é uma expressão antiga em desuso na língua portuguesa. Mas pode ser transposta para o inglês como:

• Who do you think I am?
• What do you want from me?
• What are driving at?
• What's the point?

Estas expressões em inglês chegam bem próximo daquela em português. Sendo "whataya (what do you) want from me?" aquela que mais se enquadra no contexto do seu exemplo e inclusive é o título de uma música interpretada pela cantora P!nk.