There are plenty of very good resources online to learn C or C++ so this page is not a C/C++ course but more of a list of resources that I personally think are good and that I used and still use today. I prefer watching YouTube videos over reading books or written tutorials to learn so the following resources will mostly be videos/YouTube channels.
- The Cherno and his C++ series
I personally learned C++ almost entirely with his videos, he takes time to go in depth with everything he explains and it truly helped me understand how the C++ language actually works. If you have no idea of how C++ code (so text) gets converted to machine code and how an executable file is created from this machine code, I recommended paying close attention to the fifth, sixth and seventh videos of his C++ series. If you have some programming experience, you can probably skip the videos about the programming basics (variables, functions, conditions, loops) but I recommended watching the video about variables if you come from a dynamically typed language like Python or JavaScript and are not too familiar with data types. If you have no programming experience at all, you should probably watch everything. - Jacob Sorber
Jacob Sorber's channel is a good resource to understand low-level concepts such as memory layouts, threads, sockets, system calls and more. He uses C on POSIX systems which is not the usual environment video-games run in but it will help you understand low-level concepts.