I have a crush on a guy in my karate class.

It doesn't really matter what you say. If you don't talk to him and he moves, you will always wonder 'What if?'

Offer to show him your best/favourite grip

You have common ground, loads of easier conversation starters just say Hi to him and say you see him around, pay him a compliment at some point and see how he responds.

"Hey! I'm *insert name*. How are you? How are you finding the class? When's your grading? How long have you been doing karate? Do you wonna hang out after class? Could you give me some tips to improve?"

Not all at once though.

Thanks so much for all your help! I actually talked to him, and I asked him about how long he'd been doing the art for, and he said five years and (I think) he smiled a lot and he seemed really open to conversation, and it all went great until my instructor barged in and said that that wasn't the average time it takes to earn a black belt, and J hadn't been showing up for classes a couple years ago (I think it was to dissuade me from thinking that it takes THAT long to be an expert).
J seemed pretty confused tbh, but when my instructor left, I introduced myself to J quickly and shook hands. Again, I think he smiled a lot, and seemed a bit puzzled by my introduction but told me his name nevertheless. Thoughts and ideas about what to do next? Should I approach him again or should I wait?

Thanks so much for all your help! I actually talked to him, and I asked him about how long he'd been doing the art for, and he said five years and (I think) he smiled a lot and he seemed really open to conversation, and it all went great until my instructor barged in and said that that wasn't the average time it takes to earn a black belt, and J hadn't been showing up for classes a couple years ago (I think it was to dissuade me from thinking that it takes THAT long to be an expert).
J seemed pretty confused tbh, but when my instructor left, I introduced myself to J quickly and shook hands. Again, I think he smiled a lot, and seemed a bit puzzled by my introduction but told me his name nevertheless. Thoughts and ideas about what to do next? Should I approach him again or should I wait?

Thanks so much for all your help! I actually talked to him, and I asked him about how long he'd been doing the art for, and he said five years and (I think) he smiled a lot and he seemed really open to conversation, and it all went great until my instructor barged in and said that that wasn't the average time it takes to earn a black belt, and J hadn't been showing up for classes a couple years ago (I think it was to dissuade me from thinking that it takes THAT long to be an expert).
J seemed pretty confused tbh, but when my instructor left, I introduced myself to J quickly and shook hands. Again, I think he smiled a lot, and seemed a bit puzzled by my introduction but told me his name nevertheless. Thoughts and ideas about what to do next? Should I approach him again or should I wait?