Hey Marius! I am Guix and scheme newbie myself. I can't provide you with concrete learning materials, just some tips from my journey.
I have learned a ton by working on a real project, namely, I try to port guix to a custom arm32 board using cross compilation. Cross compilation seems to be undersupported, so I stumbled upon multiple bugs, which I tried and partly succeeded to fix. Most of the time I spend reading the guix source code and try to understand what is going on. By doing so I learned a lot about how to write package definition, how to setup dev env using guix shell, how the mail driven development process works and much more. Have you considered a similiar approach for you? Maybe you are missing a package where you could provide a package definition. Or you look for a bug on the Issue tracker you could fix? For me getting my hands dirty and working towards a defined goal works best as learning process. Best regards Christoph
