first, pardon my English

hi, I'm a software engineer and I self-study at home.

I'm currently re-studying precalculus (Precalculus Mathematics for Calculus 7th Edition 2015) and i was thinking of studying other pre-university subjects in math help forum (algebra, geometry, statistics).

but my real objective is to study and learn discrete math. my problem is that i don't have a tutor or counselor to help me better understand how i should approach this. please understand that applying for a university at the moment is not a possibility.

if you had proper education and know the guidelines i'd appreciate your help. i'd really like to know which books I'm supposed to be studying. thank you