Is it worth to really review everything and do people that do deep learning professionally have always amazing knowledge about math, or is it normal to dig it up when you need it?
I could buy some books and go through them, but I'm not sure if it's worth the time given that I can invest on learning all the ML/DL things I don't know, which are many.
You probably should at least know how to do the basic stuff in numpy or whatever though.