I don’t understand anything, help.

Before anyone says, yes I listen in lesson, no I don’t mess about, yes I do my work.

But I still don’t understand anything the only subject I understand fully is maths but science I don’t have a clue. I keep trying to revise but at the end of it all I’m still at step 1. I seriously don’t get the concept of it all, I’m trying to teach myself something I don’t get. I have those CGE books, I make flash cards, I do past papers I watch videos but still it’s gone all of it what am I meant to do.