How to fix a headliner drooping from the rear

You can purchase a spry adhesive for that purpose, but it usually does not hold too long. I would find a good upholstery shop.

Headliner or upholstery twist pins... Search ebay for a wide selection of different styles and designs... Can be easily installed in a symmetrical pattern that looks quite well.... You are looking at SEVERAL dollars to have it replaced!!.. While driving, leave all windows up until you have it fixed!.. Just saying.