The German University System - becoming a scholar in the 1930's

[Forscher64]

I'm writing about German academics in the 1930's and I am having a hard time grasping the process and procedure of preparing for a university career in the humanities (languages, literature, linguistics, history, philosophy, etc.) at that time. I have German colleagues who have told me step by step how they got there in recent decades, but they all say the system has changed a lot and I don't know anyone who knows how it was back then and nothing I have been able to find on the internet goes into the kind of detail I need, so I am hoping someone here will be able to help.

Looking at the biographies of particular university professors and other academics from that time period, it strikes me that most of them: a) seem to have "studied" (rather than majored in) about three or four subjects at several different universities before b) going to another place to write their doctorate under a specific professor in a relatively short period of time, and then c) often writing their Habiltationsschrift quite soon thereafter. Thus, a good number of people I've studied seem to have been fully qualified when they were quite young, still in their mid-twenties.

So, is this how it worked back then?

1. You attended Gymnasium until you were 18.
2. From about 18-20 you spent a year each at two or three different universities taking classes in related areas until you got an idea for your thesis. [Question: did you get a degree? If so, what?]
3. You then got a recommendation for a professor, usually at a different university, under whom you would not study in a program, but simply write your doctoral dissertation under his direction and guidance, and thus earn your Ph.D. by the time you were about 22 or 23 [Questions: how often would you meet with him in an individual tutoring fashion?]
4. After that, rather than having to wait about 5 years as currently seems to be the case, you could simply repeat step 3., becoming Dr.Habil. by the time you were only about 25.

Can this possibly be correct? Again, I can only surmise so by looking at the biographies of several scholars whose works I have studied, but I am having a hard time wrapping my head around the process and would love some confirmation that it really was so.