I am a total beginner too. However, I will try my best.
I tried to solve a similar problem as you, and have tried a few things.
So far I am unable to make any opensource model work for this (or in general).
However, I saw somewhere in OpenAI API docs that you can upload documents and their models will answer questions from your documentation.
I have successly been able to use davinci model playground to answer questions based on the context (included in the prompt). In their playground there is a “chat” preset. I used that and modified it to my use case.
I havent deployed it anywhere yet, but as an experiment my mind was almost blown!
Because we both are working on a similar problem, I would like to stay updated on your progress too.