First of all sorry for posting link because I need 10 reputation to post images.

Hello, I’m currently novice at neural network, and I’m trying to code neural network from scratch (on my own). I’m trying to make a neural network structure like this:

The issue, which is tough to me, is backpropagation; In my neural network I’m using RELU as an activation function and MSE to calculate loss. So I tried to derivative it.

here is all my derivatives:
https://i.sstatic.net/GPuO3JNQ.png

but I’m struggling at how to compute those function because they may be different in dimensions
and do i have to compute this
https://i.sstatic.net/gMtBWRIz.png

please help me this is the first time i have asked in stackoverflow.
Thanks!