3Blue1Brown:
https://www.youtube.com/playlist?list=PLZHQObOWTQDNU6R1_67000Dx_ZCJB-3pi
what is NN
https://www.youtube.com/watch?v=aircAruvnKk
backpropagation
https://www.youtube.com/watch?v=Ilg3gGewQ5U