It's nothing more than the chain rule...University level it is not...the engineering aspect is the non trivial part IMHO...
While many learn calculus in high school, many also don't get it till uni. Not everyone is at your level, or took your same path, and that's okay. Don't shame people for not knowing when they're trying to learn.
I ask because it’s pretty difficult to get through the math of backprop without a firm grasp of these. The Python part is trivial by comparison, the main difficulty being the matching of dimensions.