Hi,
there can be different ways to increase the test accuracy.
If your training accuracy is good but test accuracy is low then you need to introduce regularization in your loss function, or you need to increase your training set.
if your training accuracy increased and then decreased and then your test accuracy is low, you are over training your model so try to reduce the epochs.
if your both training and testing accuracy are less then try to either change your model architecture, or increase the training data or decrease learning rate or increase the number of epochs.
Feel free to ask for any clarification.
