I am a German National working in the US on a H-1B Visa. I am currently planning my retirement investments (I am in my twenties now) and I am trying to understand the tax implications.

I have a private retirement plan in Germany as well as the option to establish a 401K in the US (tax-free contributions). If I go back and live permanently in my home country when I reach retirement age and withdraw my US 401K contributions from there, will they be taxed in the US or in Germany? If I will concurrently withdraw contributions from my German retirement plan, do I file for taxes on those in Germany or do I file for both contributions/ earnings in one country? I can not imagine that I will get to pick the country with the lower taxes?!

If the money from the US 401K will later get taxed in Germany (with much higher taxes than the US), I might be better of to pay my taxes in the US now and transfer it to Germany now to invest there.

I appreciate your advice!