Re-iterating what others have commented: quick-wittedness isn't "thinking fast" in the same way as you think slow, it's a different variety of thinking that comes with practice.

I've always been a slow thinker, & always discounted quick-wittedness as a skill others had innately. Recently I've found myself being a bit more quick-witted & what's remarkable it's not something I "think" about (at least actively). It's something that comes out from a different place (subconscious?) & does so more & more with practice. E.g. take referential connections: I used to be amazed that people could connect things in conversation so quickly because my mind simply doesn't connect things that quickly - but I think it's more like the pre-connected reference bubbles up from deep in your subconscious pre-made; you don't think about the referential route.