Hallo,
I work in the US on a L1-Visa (I'm from Germany) since two years and most likely will leave the US end of this year. I get my salary paid by my German employer and get all benefits from Germany, absolut nothing from the US. I do pay taxes in Germany. Do I also have to pay taxes in the US?

Yes. Income earned in the United States on a L-1 visa is generally subject to U.S. taxes, unless specifically addressed and exempted in the U.S.-Germany Tax Treaty.

It is likely that you will get a credit on your German tax return for taxes you pay to the U.S. If not, then you can claim a credit for German taxes paid.