Hey there @mburajamahoze,
Welcome to the Wefugees community and thank you for your question :-)
If you are in Germany and want to apply for asylum, you have the right to do so. Asylum is a right that is protected by the German Constitution. Since your visa expired, it is advised you do so quickly, to avoid being in Germany illegally. Here is some more information on claiming asylum in Germany by the BAMF: http://www.bamf.de/EN/Fluechtlingsschutz/fluechtlingsschutz-node.html
And an article by Deutsche Welle on how to claim asylum: https://www.dw.com/en/how-to-apply-for-asylum-in-germany/a-18723501
Also have a look at these threads from our platform, which can be helpful to understand the process:
Can I apply for asylum with a Schengen visa?
Can I apply for asylum in any country in Europe?
I hope this information helps. Please feel free to reach out to us again if you need any further assistance!