The two you linked are different communities, with different rules, different content and moderated by different people. They just happen to have the same name.
What federation lets you is view and interact with communities that are hosted on another instance, for example:
If you dont like the rules or userbase of lemmy.ml, you can choose one of the many other instances, which are administrated by different people and have completely different rules. There are also some instances which have the slur filter disabled.
Lemmy maintainer here, its great that you are interested in our project. However it would be better if you linked to https://join-lemmy.org/ instead, which is the official project website and includes an extensive list of different Lemmy instances with distinct communities and rules. What you linked to is just one of these instances.
I studied Computer Science in Germany, and I didn't use a single book during my entire bachelor. The way it worked was professors always put the slides from their lectures online, so we could reference them as sources. Sometimes, additional references or texts were available online.
In addition to lectures, we had weekly classes where we applied the concepts from the lecture in practice. Exercises for these classes were also available online.
All of this material was free for students, and created by the professors and instructors specifically for the course.
I don't see how Berlin could be considered Cyberpunk at all. Sure there are some modern buildings, but most of it is at least 50 years old. And there's no real high-tech.
I'm personally using LinageOS together with microG and F-Droid. MicroG is necessary if you don't have Google apps installed, to get push notifications. Unfortunately, it is still rather complicated to install.
Google is really bad with this. This is especially annoying as an expat who doesn't speak the local language. I'm really glad I switched away from Google a long time ago (using startpage.com for search).
What federation lets you is view and interact with communities that are hosted on another instance, for example: