There are 2 books that explain partial dentures really well. They were part of a BDJ series of articles back in 2000/2001 (I think)
You will have access to the articles and the book via your library login, so don't need to buy them. The library will have physical copies too.
I have also found the first book online:
https://www.researchgate.net/publication/12245735_Removable_partial_dentures_an_introduction
Please read through the articles then ask any specific questions you may have. Alternatively, we can go through a chapter per week if you would prefer.
• Resistance= the ability to resist oblique forces directed at the restoration
• Retention= The ability to resist displacement forces along the path of insertion