Re: Where should I start from

Here is a proper beginners guide to start learning about bitcoin.

Here's the knowledge iceberg, IMO:

Level 0: Start off by visiting bitcoin.org.
Level 1: Learn me a bitcoin: https://learnmeabitcoin.com/.
Level 2: Mastering bitcoin: https://github.com/bitcoinbook/bitcoinbook.
Level 3: Ask questions in here and in StackExchange. Also, study the devguide.
Level 4: Documentation of Bitcoin Core: https://doxygen.bitcoincore.org/index.html.

General course around cryptography can also be helpful: https://crypto.stanford.edu/~dabo/courses/OnlineCrypto/.

I strongly support BlackHatCoiner's list of resources.
For anything technical (especially since this is posted in Development & Technical Discussion), I usually refer people to https://learnmeabitcoin.com/ and https://en.bitcoin.it/wiki/Main_Page.

For anything 'meta' (forum-specific), this post by Lauda is very helpful: https://bitcointalk.org/index.php?topic=1689727.0