Loss is decreasing but val_loss not!
This indicates that model is not generalizing (it is over-fitting). Few options are :


Get more training data 
Reduce complexity of model (Number of LSTM layers, complexity of dense layers)


Andrew NG has a good video on this topic : 

https://www.youtube.com/watch?v=OSd30QGMl88 

A tutorial specific to LSTM : 

https://machinelearningmastery.com/diagnose-overfitting-underfitting-lstm-models/