We have Lamy, Pelikan, and Montblanc.
Of these, I only own Lamy pens. Lamy stands out by virtue of making affordable and very popular pens like the Safari and AL-star. They also make the all time classic, the Lamy 2000.
Montblanc is made in Hamburg, Germany. It is not (contrary to common thinking) made in Italy. I tend to look sideways at Montblanc pens, viewing them as overpriced status symbols. The Montblanc 149 is called the "diplomat pen". It is a pen to own if you want to strut and look like a CEO or some kind of bloated millionaire. The 146 is a more practical pen in their lineup, but an even better choice is probably a Pelikan M800.
Pelikan pens are well regarded, but I know almost nothing about them. Some are made in or near Hanover. Others are made in Asia, Mexico, and elsewhere -- so you really cannot regard Pelikan as a "German pen".
The following review video is interesting, but almost sticky sweet with the fellow talking in what sounds like polished advertising copy: He also has somewhat of a clickbait title, claiming to declare the best fountain pen from Germany, but then ending the video with pros and cons of the three pens and telling you to pick the one that is "right for you".
Tom's Pen Info / [email protected]