You're gonna love "Mastering Bitcoin" book if you still haven't read it.
Here are some resources that you should consider reading:
- Mastering Bitcoin: https://en.bitcoin.it/wiki/Mastering_Bitcoin (Download pdf/other format) - I can't recommend this enough, this explains Bitcoin from the very basic ELI5 concept to the most technical answers.
- Bitcoin Whitepaper by Satoshi Nakamoto (Some info were unimplemented but most are still relevant): https://bitcoin.org/en/bitcoin-paper (Select language to download)
- Bitcoin Core RPC: bitcoincore.org/en/doc/0.19.0/rpc (Select from the command list on the right) - Commands you can "play with"
- Developer Documentation (most are technical): https://bitcoin.org/en/developer-documentation - use the links and search function.
I found this youtube channel and it seems really helpful:
https://www.youtube.com/channel/UCj9MFr-7a02d_qe4xVnZ1sA