Can’t flirt to save my life, help?

So I suck at flirting. Im talking to this guy I like and when we’re having a normal convo I’m alright but whenever he flirts I have no clue what to say. Example:
Him: Do you have a Valentine’s?
Me: I don’t wbu?
Him: Nope, maybe next year though 😉

What do I say to that? LOL
Can’t flirt to save my life, help?
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