Germany has quite a decent network of public transportation and usually can get you from point A to B. However, understanding all of the various options, how they work, and even when they work is not always the easiest.
I've been using the system for more than five years and I am constantly learning new things about it. For those who are new to living in Germany, it's a steep learning curve.
Live Work Germany wrote a guide about using the trains, buses, subways, and street cars of Germany. It's very useful to help unravel the mysteries of the transportation system; you can read it here.