Ah I see, so the challenge is that you can have a question like “Does it run on Windows?” which could apply to multiple products (I’m assuming you can’t filter the passages by some product ID)
If you happen to know the sequence of questions in a given chat, I wonder whether you could do something simple like treating all responses between two questions as potential answers which you can then rank with something like TF-IDF
If not, then an alternative would be to label some data with e.g. “question” and “non-question” and train a simple classifier. NER could certainly help and for that there’s a nice tutorial here: https://colab.research.google.com/github/huggingface/notebooks/blob/master/examples/token_classification.ipynb#scrollTo=545PP3o8IrJV 6