My head hurt just reading the list of subjects.
OK, so I'm not bad at Mathematics so I chose :- General Mathematics, Lecture notes of William Chen concerning First Year Calculus.
Right understood first paragraph.
Ignore class references as not relevant.
Go to Chapter 1 and read subheadings.
It's no good. Pass the Paracetamol. If the contents list gives me a headache I know I am not cut out for academia.
It does look like a good reference site though, text books were always a drain on my finances when I was still in education and I doubt that they have got any cheaper.