I would hire a tax person that focuses on expat taxes and has experience with German residency. These things are highly nuanced.
Things that are not taxed in the US (your 401k, IRAs) may be taxed in Germany. Is there a tax treaty between the 2 countries that decides which social security system you pay into? Etc...
Most likely you will have a $0 US tax liability - getting a credit for any tax paid in Germany.
You can't exceed the income allowed by the foreign tax credit (you can exceed the Foreign Earned Income Exclusion amount.)
Any excess can be carried forward and applied to future US tax bills, assuming you return to the US within 10 years.