I read the Foundation Trilogy probably 30 years ago. Very complex to grasp then, while marriage and career took a lot of my attention. I still have the book and may take another read.
Asimov wrote several prequels and sequels to ‘Foundation’. They were not written in chronological order, so there are some inconsistencies in them, but they spanned 50 years of his life, so it is to be expected...............
https://en.wikipedia.org/wiki/Foundation_series