Stay for the purpose of tourism
You are very welcome in Germany.
If you have entered Germany with a Schengen visa, you may stay in Germany for 90 out of 180 days. The Schengen visa cannot be converted into another residence permit or extended.
If you were able to enter the country without a visa, your stay is also limited to 90 out of 180 days.
If you would like to stay longer in Germany and have entered the country with a national visa, apply for a residence permit at the local immigration authority in Germany.