Use the "scribble technique" for your revision. It's basically reading a page or so of your textbook/revision guide and once you've remembered the information, you then write it all down FROM MEMORY. Hope this helps!
Nahh I'm kidding. I'd recommend going through some revision guides first to understand your course. If you don't have any handy with you, just go on google and type in "GCSE Biology Combined Revision Guide PDF" and usually some schools have revision guides that they upload online for free. Or use https://www.primrosekitten.com/products/gcse-revision-pack
Primrose Kitten revision guide is free, just add it to your cart and click proceed. You don't have to enter any credit card details or whatever, you'll just get the download link. Then after you've read it, and as the comment above said ^^^^^^^^^^^ Freesciencelessons is a really good youtube channel for science.
You can definitely learn all the content in a week if you put in an hour or two a day, and then you have more than enough time for past papers. Or spend 2 weeks understanding and getting the content down, then just do past papers.