I'm very curious how people know some many programming languages and I can't even learn one?

Because they can't? There's a reason people are in categories like front end, backend etc

I think the answer is in your question. You say, "I can't." Of course you can. Don't mistake memorizing for learning. Only a few gifted people can memorize a language, the rest of us do, and do, and do, and over time we get experience. Those algorithms that we use on a daily basis, we eventually memorize; the rest, we Google. Yes, you can.

Once you learn the basics of programming, you can apply the same principles to any other language.

With different languages, the vocabulary may change, but the grammar tends to be pretty much the same. Because of this, the more languages you learn, the easier it is to learn another.

Practice.