Hello @Thrasso00,
There are 3 new videos and 2 new optional labs on backpropagation now available in the MLS. Backpropogation is the technique for calculating how each weight in a neural network is updated. Please check out course 2 week 2 for the new materials, or you may click this link to go to the first video.
There is also this video from Andrew which talks about forward and backward propagation in one video.
After you watch the videos, if you want to set up a simple NN and a simple dataset and write down step-by-step how forward and backward propagations are carried out, I can help check your maths.
Cheers,
Raymond