I am trying to learn more advanced C and so I think learning about all these things are implemented efficiently in the standard library (by whomever) would be a good learning experience. I am also currently starting a big project where eventually I will need to implement some of the standard library myself, so I especially would love to know how at least some of it is done, and how it is done efficiently.

thank you in advance.

If no videos exist on the topic (which I sort of expect since it may be a niche topic) then a book or internet site would be okay too. I just learn better when I can hear an explanation rather than read one.