How to make a neural network generalizes better?
First make sure your dataset is labelled properly in 5 distinct classes from 0 to 4 and no more.
Then add dropout layer in between each layer with prob of 0.1 and gradually increase till 0.5 until you find  a good val score.
In your optimizer add weight decay term with value around 0.1.
Find some appropriate regularizer for your data type online.