Need advice and help for As level Business

Hi
Things aren’t going pretty well for me. I have taken a gap year due to personal reasons. I was originally A science student but have to switch to Business. And it’s new to me for AS level and in 4 months I’ll give my exams.
Can someone please help me out in how to study. Like from where should start. Or should I straight up go for As level Business Topics?
I did get an overview about business studies but still it’s something very different and overwhelming to the point that I’m so anxious I might not be able to pass. (Again I have been and A grade student for Sci but business is the opposite)
Can someone please help me out how can I just pass in the exam. I am satisfied with C grade (self study)
And should I go through alll the IGCSE notes??