What's the current best resources to learn assembly? So that I can understand output of simple functions. I don't want to learn to write it properly, I just want to be able to understand on what's happening.

https://godbolt.org/

You can select the assembly output (I like RISCV but you can pick ARM, x86, mips, etc with your choice of compiler) and write your own simple functions. Then put the original function and the assembly output into an LLM prompt window and ask for a line-by-line explanation.

Also very useful to get a copy of Computer Organization and Design RISC-V Edition: The Hardware Software Interface, by Patterson and Hennessy.