There is a problem with the GPG key. I don’t know why, but I would not use that script to install Docker anyway. It should work in a test environment, but you can follow the official guide to install Docker CE on debian
which includes installing the GPG key
I also formatted your post. Please, always format your posts in the future following this guide: How to format your forum posts
It is also good to share some thoughts additional to the shared code. That catches more people’s eye than a single code or log