Great vintage movie. With its own special natural portrayal of porn. A film with a plot and even an interesting story and, most importantly, in excellent quality, which is difficult to find in retro films.
The 1978 feature "Debbie Does Dallas" is probably one of the most famous classic porn films.

It begins with the fact that cheerleader Debbie urgently needed money to move to Dallas in order to continue her professional career as a cheerleader. parents don’t give money for it. Her friends support her and they start earning money for the trip by providing sexual services.

Imdb link: https://www.imdb.com/title/tt0077415