The whole idea with Interrail is to explore other countries than your own. For many years you were not allowed to travel in your own country at all with the Interrail pass. Then you only got a discount on the travel to/from the border.
At present there is the outbound/inbound rule that allows you to travel on a maximum of two travel days in your country of residence.
As you already use your travel days in Germany you can't use the pass in Germany any more.
If you want to travel in Germany you can use the 9 EUR ticket throughout August.