I separate my narrator from my main character's voice. I do not write in first person, I write in 3rd person limited, with a deep POV. (Deep 3PL). Meaning, for those unfamiliar, my narrator knows the thoughts, sensations, emotions and memories of my one main, POV character, (that's "deep") but "Limited" means the narrator has knowledge of ONLY this one character: So the reader doesn't learn the thoughts and feelings of any other character, which in writing has the advantage of allowing my POV character (and reader) to be deceived, or to not know secrets of other characters, etc.
The 3rd person separates the narrator from the POV. So the reader reads
Lisa ran her standard route. Half mile to the post office, three quarters to the Walmart, back by way of Grantham Pass, she liked the houses there. Like running through a manicured park. Couldn't afford them. Ever. But today the houses and landscaping didn't even register, she ran automatically, her mind occupied by Roger's transform equations. She wanted them to work, they had to work, but there was something missing, just out of her grasp.
The advantage of this approach (to me) is the narrator can describe what the POV character is thinking, in a way that (IMO) no person would plausibly think about themselves. I can describe the kinds of visual memories that accompany our experiences. Your character picks up the muleta, then we need no technical description of what it is, just her brief flash memories of how it is used, when she was taught how to hold it and yield it. She must get ready for this fight, I imagine. There must be moments of the fight where she thinks about what she is doing, and the narrator can explain why, what is going on in her head, and how she learned it.
Those are the advantages a deep 3PL offers. Your narrator voice doesn't have to reflect either your POV character's inner voice or outer voice, if those differ. For example, in one of my stories, the POV character was raised in a religious system that uses an older form of English, she thinks (we see her thoughts in italics) and speaks (in dialogue) that way. But my narrator does not. The narrator relates the tale in normal English, and has their own voice, a wider vocabulary, more eloquent and descriptive than any character in the book. (I do avoid the narrator using anachronistic analogies or metaphors for my settings, e.g. they can't compare something to a pocket watch if those don't exist in the world.)
This makes the narrator capable of translating the thoughts of the POV character. I seldom do that directly, but the translation can be done using how the POV character understands something:
They were harvesting apples, forty pound bushels for the adults, and a quarter that, pecks for the kids. Marie had a fond memory of that, one of her first, struggling to get her peck to the presser, only able to carry it about four feet at a stretch. She'd been so proud to finally get it there. but her favorite job at harvest had been picker, at ten she was light and small enough to navigate the thin limbs, to reach and disconnect the further apples with her long picker's fork, to a catcher below. It was death-defying, and thrilling.
The point of this immersion is the narrator can casually define in context things the reader may not be familiar with, like bushels and pecks. Also the job titles, presser, picker, catcher. You know pretty much what a picker's fork is without me describing it in any detail; obviously it is long stick, forked at the end, used to push an apple and break stem from branch.
But also, by tying this to memory and Marie's emotions, we get a micro-scene so the definitions are not just a list of dry terms to memorize. The relationship between Bushels v. Pecks is Adults v. Children. Pickers are around ten, old enough to climb, light enough to not break branches. If Marie did not have personal experience harvesting apples, I'd give her a foil, somebody to answer her questions.
You can do the same thing for your matador; or some combination of methods, memory and explanation to a foil new to the game, or an outsider unfamiliar with the terminology: Friend, lover, acquaintance, a kid, their own kid.
The trick (I think) is tying the delivery of this information in with emotions. In the first example, Lisa is pre-occupied, but the narrator doesn't have to be, her normal enjoyment of Grantham Pass is described, even though she doesn't experience it in this scene.
Likewise in the second; Marie's memories tell us what is happening, the 3rd person narrator defines terms, but the whole thing may take a single second as these memories flash through her.
I find these things difficult and awkward in first person. in Deep 3PL we can still get all the advantages of first person, through directly stated thoughts or dialogue. I use both. But I'd give your narrator their own voice, so they can slip in the clues the reader will need to understand the terminology.