So C is basically assembly with a bunch of syntactic sugar on top. It manages a lot of the book keeping and boilerplate, but at the end of the day there's not a ton of difference between them in terms of the abstractions it provides. If you know assembly learning C is a piece of cake. If you don't you're probably going to take a while to really wrap your head around pointers and the myriad ways C can use them for great and terrible things. Beyond pointers (and race conditions if you're crazy enough to do multithreading in C) the rest of C is super easy because there really isn't much else there.

Rust on the other hand is a much higher level language more comparable to something like Java, C++, or Python. It gives you a lot of tools to solve complicated problems but unlike Java and Python and like C++ it still gives you the option of working at a low level when you need to. The big advantage it has over C++ is that it learned from the many mistakes C++ made over the years, and the borrow checker really is a unique and powerful solution to both memory management but also crucially concurrency problems.