Rasa Response selector training issue

I am building FAQ Bot using rasa but i am facing training issue with Response selector.Diet classifier training taking 40min with 20k FAQs and accuracy=0.99 but response selector training taking 1 day for 100 epoch with GPU and accuracy is very low 0.048.can you please guide me how can i improve this response selector part. Why its taking so much time for training. When i am using small data like 100 FAQs its working fine with same code. When i used 20k FAQ .for any question its giving only one answer.i am using RASA 2.1.