In total, some 14 million people or more in Germany have a non-European background. Many of these non-Europeans do not yet possess German citizenship and those that do are often loosely connected to Germany.
Solutions:
The simplest and most efficient method of reducing the non-German population of Germany would be to enact widespread cancellation and non-renewal of visas. Germany has suspended all immigration in recent times, in fact. During the COVID-19 pandemic, the German visa system was largely stopped and inflow into the country dropped dramatically.
This same process could be used again, under another guise, in order to suspend the issuance of new visas and or renewal applications. This process would see the visas of 43% of the non-European population of Germany canceled and with modest levels of immigration enforcement, this step would dramatically lower Germany’s non-European population.
The next step is to deal with immigrants who have falsely acquired German citizenship and can be denaturalized according to current German law. Germany has seen notable rises in the number of fake paternity claims which has enabled thousands of immigrant women to be naturalized in Germany. Similarly, marriage scams operating across European borders in Germany and Denmark (as simply one example) bring thousands of people into the country a year under false pretenses, many of whom are later naturalized.
Based on reports from the German government itself it is likely that hundreds of thousands of foreigners have entered Germany through the family reunification system and falsely been granted citizenship which was then extended to their decidedly non-German children as well.
Conclusion:
While the Germans may not be able to deport every non-European in their country, a comprehensive policy of visa cancellation, visa non-renewal, and investigation into widespread citizenship fraud could bring about the repatriation of well over half of the non-Western populace.
Ethnic Germans would rise to a proportion of the population much closer to 75-80%.
It is from this initial wave of policy action that the German nation could then assess the integration status of the non-European citizens who remain in Germany and decide whether laws should be further changed in order to facilitate voluntary repatriation of this population.