When trying new things, we all feel unsure. The next time you plan something new, you could watch some videos so that you have a bit of framework for the activity.

You don't understand it is all, there's nothing wrong with that. We're just not absorbing it in the same way is all, and in my experience it depends on the thing being tried, with it being our way of not looking too much into things, which is the opposite issue. Your examples are understandably difficult anyways, I can't even swim if that counts as a slow learning issue.

Maybe you're more introverted and tend towards learning in an autodidactic way?

Not being like all the other people isn't necessarily a bad thing. Yes, it's difficult to be different. But we should embrace being human and diverse. Everyone learns at their own pace. Some people learn better by watching and imitating, some people like to understand things down to the core and can't just "do this and do that and you're done." And there are different learning styles anyways: Auditory, Visual, Tactile, ...

I just wanted to say you're not alone with that. I also regularly fail to remember dancing steps, when someone shows me how to assemble furniture or do some task. I can't for the life of me remember driving directions. I'd much rather get handed an instruction manual and I can read it at my own pace. Everytime I get what I need and what matches my learning type, I can excel at things, so it's not a lack of intelligence.

And it works, too if you're taught 1 on 1. So you can ask your "instructor" to slow down or speed up things you already know. It's just difficult in group scenarios. And I don't think there is a way around speaking up and letting them show it to you once more. But I think most people should theoretically be able to relate. Other people struggled in maths in school and had things explained to them over and over again, which was super boring to me. But we all grasp different concepts in different amounts of time and we sometimes need to be taught in the way that is right for us individually.

And a last word to climbing: Getting it almost immediately isn't the important part of the knot. The important part is that you never fail to do it correct in the years to come. Where I learned climbing they hand you a scrap piece of old rope and you can practice at home. And the week after you need to demonstrate that you're able to do the knot and check it for correctness. I've been with the (boy) scouts for years, so I could already tie the knot perfectly.

(Edit: "Learning style theories have been criticized by many scholars and researchers. Some psychologists and neuroscientists have questioned the scientific basis for separating out students based on learning style. [...] Many educational psychologists have shown that there is little evidence for the efficacy of most learning style models, and furthermore, that the models often rest on dubious theoretical grounds." Source: Wikipedia)

Do you maybe have ADHD or anxiety? That would be a reason for it

Sounds a like a combination of fear of failure and anxiety around social settings. Failure should be, and usually is, a part of learning, which is something I'm working on internalizing for myself 😅 but it sounds like you're also putting a lot of pressure on yourself not to make any mistakes, which is unrealistic and also sets you up for immediate failure if you get into your own head about it.

Generally the answer to any fear related issues is exposure. If that idea is horrifying then its especially important, and you'll need to start small. But letting yourself experience the source of fear enough times for your anxiety to go up, observe the way it comes back down and that you're okay, and you start to feel safer in that kind of experience

But if you do too much at once you'll often make the problem worse. If you've got good friends you can ask, maybe share what you're having a hard time with, and see if y'all can learn origami together or something with people you consider safe. Feel out the anxiety, and when you fail, notice that you're stjll okay :)

Investigating fear of failure and exposure therapy online may yeild helpful that really helps with perspective and practical approaches to dealing with what you're facing

Sending love and hugs, thats a crap experience

One thing that helped me is to imagine the worst, best, and likely scenarios to occur. Like tying a knot. Worst: I cannot do it, everyone there laughs at me and the instructor says I am the dumbest person they've ever seen. Pretty unrealistic. Best: I do it perfectly the first time, help everyone else, and they all think I am some sort of genius. Likely: it probably takes me a few times, but I'm certainly not the worst the instructor has seen. Everyone else takes one or two tries and mostly sympathizes that the knot isn't trivial to learn.

I'm sometimes like this too. Everyone learns differently. Different ways, different speeds. A common example is not understanding some math concept, until someone explains it differently and suddenly it clicks. Don't be afraid to speak up when you aren't understanding something, or just need more practice. Also, depending on the class, ask if you can get some materials or resources in advance so you can preview them on your own.

Actually, it's the same for me.

It is because others put up a lot of pressure to "get it immediately". I'm not stupid (I swear) but it takes me like a solid 2 minutes sometimes to understand something. Others expect me to get it in 5-10 seconds.