chatgpt help advice via api

I need help with advice how can I use API that we build to have PRIVATE data, and we wish to acomplish with it:

Upload user manual in pdf or word and ask question so it can answer back (similar like customgpt.ai)
upload database scheme so it can return microsoft sql query based on sentance like: show me sales per year and product.

Thanks.

please apply only if you know how to accomplish one thing.