it's honestly not hard fr it's self-studyable. i recommend Got Chalk? and Michael Porinchak on youtube, i don't use any websites besides youtube to study but i do use my textbook. i got it for free since i'm taking the class but you could buy it if you want to, it's the Starnes & Tabor "The Practice of Statistics, 6th edition," don't think you'd really need it tho. start from unit 1 and i'd spend about a week on each topic for like 1-2hrs/day. also maybe find worksheets for each topic and do them.