Upvote:4
I am assuming you are entering Germany from outside the Schengen Area.
In most cases your passport must be valid for the entire time you will remain in Germany (thus in the Schengen Area). There is a passport control when both entering and exiting the Schengen Area and you cannot leave on an expired passport. As you are a German citizen, Bundespolizei will not care about the expiration of your passport in June when you are entering Germany, as there is no legal need for you to return to where you came from.
Some countries, however require that your passport is valid for at least X amount of time when you are entering or in your case are re-entering. You will have to make sure, you can return to the country you came from. Entering Germany will not be an issue.