Contributing to Rails

Hello,

I’ve been using Ruby on Rails for some time now as a developer and I’m
interested in contributing to the project.
I’ve read over the contributing documentation
(Contributing to Ruby on Rails — Ruby on Rails Guides)
and
have the development environment set up on my computer.

However I’ve had trouble finding a good issue to get started on. Mostly
because I’m not too familiar with the inner workings of some components,
such as ActiveRecord or ActionPack.
Are there any good resources or overviews on how these components are
structured? Or can someone point me to some simpler issues suitable for
beginning contributors?

Thanks,
Ernst Rullmann