How to learn blockchain development.

The blockchain technology is not easy to understand.

In particular, there are two concepts you should first have clear in your head. Those two concepts are cryptography and distributed computing.

So if you want to start learning I would advise you to start with something more comprehensive on what are hashes, blocks, distributed computing, and blockchains.

For example a good explanation of what are all those concepts is given here Blockchain Demo There you can understand what are SHA256 cryptography algorithms are how it plays a role in tying the blocks together in a chain, thus the blockchain.
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Then you can continue with a more technical content. A course such as the following Blockchain and Bitcoin Fundamentals | Udemy (https://www.udemy.com/blockchain-and-bitcoin-fundamentals) might give you a better idea of the blockchain technology and its concepts as a whole. I got my certificate of completing the course recently so I can recommend it without hesitation.

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Another resource you can use in your learning path is also the Hyperledger project. Here you find it Hyperledger is a Linux Foundation project and is about blockchain for business applications. Now there is a free course on Hyperledger taught by EdEx and you can find it here Blockchain for Business - An Introduction to Hyperledger Technologies (https://training.linuxfoundation.org/linux-courses/system-administration-training/blockchain-for-business-an-introduction-to-hyperledger)
I think that this is enough material to start with. However, during your learning and experimenting with blockchain, you will have to go back and reread what you have learned many times as blockchain concepts are not easy to grasp. Happy learning :-)