In that case you should contact a professional who has done this thing before. But be aware, it’s quite expensive. This site, for example, charges 749 €.

The IRS has a special procedure for this case called “streamlined procedure”. Unfortunately it’s a little complicated and you have to pay close attention to all the required details.

Since OP was never an American resident or paid taxes, he or she shouldn’t need to file taxes or be flagged on a system for anything anyway.

Unfortunately the US is one of two countries that requires all citizens, regardless of past or present residence or employment, to pay federal taxes.

Always enter and exit the US with your US passport. Not doing so is illegal.

For anything else, use your German passport, especially in the EU. That’s what I have been doing for years.

I don’t know if it is an issue for immigration, but you absolutely are required to file taxes every year and can get in trouble if you don’t. There’s a “streamlined procedure” that you can do if you’ve never filed taxes to start filing without incurring any fines or penalties.