The United States have different rules about exactly how one obtains an engineering license, but the general process is the FE exam, a few years of work, and the PE exam. Suppose one then wishes to practice engineering in Germany. What are the legal requirements for doing so?
Unlike within the United States and the PE license, it doesn't appear that it's possible to receive an EUR ING license by direct comity. EU Engineering licensing is handled by FEANI, and on their EUR ING page they state:
Application is open only to individuals if they are members of an engineering association represented in FEANI through a National Member
But it may be possible to join one of the German FEANI members and see if they can support a reciprocity or comity process.1
1There are other member organization in other countries, but your question specifically mentioned Germany.
Digging a bit deeper, it does appear that there may be limited cases where an EUR ING will be awarded based upon sufficient experience as a professional engineer. Take a look through the FEANI EUR ING guide, in particular Section 5 which details the minimum requirements. Most of the cases cover qualifications based upon an education received within an FEANI member country. Section 5.4b deals with special circumstances and provides the potential pathway that you could receive an EUR ING license.
Nevertheless it is possible to consider such alternative routes. Very strict procedures, however, have then to be followed, (see 7.1), and the applicant must have at least 15 years of Professional Engineering Experience recognized by FEANI.
So it does appear to be possible, but again, it's not as simple as the comity process within the United States.
Take all this with a grain of salt. I work in Germany as an engineer and don't have any special license sides my degree, but I'm employed and your situation may be different.
Generally, engineer is a free profession in Germany. This means, if you are an engineer (have an engineering degree from a university or a university of applied science), you can freelance as an engineer. Each state has an Ingenieurgesetz that states how to handle foreign degrees. Mostly, if the degree is equivalent (Master/BA of engineering) you can request the right to call yourself an engineer (But I don't know yet where).
Additionally, I think for certain tasks in civil engineering you have to be part of an engineering association.
Lastly, if you work with a company, you generally don't need a special license (for example to sign of plans)