How and what resources can I use to understand software engineering and computer science as a whole better?

I am a self-taught front-end web developer. I have worked in teams and build built projects on my own. I have been able to solve technical problems and blockers by simply googling. However, I still feel a lot of emptiness. like there is a lot I do not know nor understand in computer science. I have simply been a tool user. learn tools like javascript and CSS and react and styled-components and web-pack, and sass, etc., and all these get the job done. However, I want to understand the core concept of programming. not just learning and making use of tools. I want to be able to look at a block of code written in any programming language, and understand what is going on within that block. even if I don't understand the syntax in itself.

simply put, I want to go low level, I want to understand the core of programming, what is happening under the hood when a program runs, how it all relates, why javascript is single-threaded, why C is faster, why JavaScript is an interpreted language.

How do I pick up this knowledge, please? (I'm not sure I constructed the question well but please, do answer to the best of your abilities)