Let me get this off my chest right off the bat: Keras is all you need for 90% of neural network applications. Before jumping in, you should understand what is going on with neural networks(watch 3Blue1Brown's videos).
Ideally, you can understand all the math behind them and code a basic one from scratch (read Nielsen's Neural Networks and Deep Learning).
But for most cases, even understanding is unnecessary with all the pretrained models frameworks ship with nowadays.
But, assuming you're not a n00b and you need to do more beyond just classifying 2D images or recognizing characters, here are the Deep Learning/ Neural Network frameworks can best fit your use case.