Great to hear it's helped so much. Since you have already paid, you automatically have access to lesson 11 and all future lessons when they are released.
You can download lesson 11 via your 'My Library' list. Click on the arrow next to your username in the top right corner of your browser to find your library of purchased games/software on itch - the Let's Build A Platformer! Course will be there if it's already been purchased.
I am still working on lesson 12 and up. I release each lesson as I complete them and will update everyone as soon as I can. It takes me around 4 weeks to complete each lesson. Thanks for your patience!