Its running on CPU and that’s why its slow.  Deep leanring models don’t support AMD Radeon GPU.  They only work on Nvidia GPUs.  This is the same for both Tensorflow and PyTorch.
Because the network is training using CPU, Deep models (with many CNN layers as here) will be slower than shallow networks.
I would suggest you try this in Google’s Colab environment.  Please choose Runtime → Change RUntime as GPU in https://colab.research.google.com/ 3