I am a Philippine passport holder and hold a Schengen Short Stay Visa with duration of 13 days. I intend to get married to a German citizen. Is it possible to apply for extension of duration of stay to maximum possible 90 days (or beyond that)? How can this be done legally while waiting for the processing of marriage documents which will surely take time?
To marry your German fiancé(e), you should follow the procedure outlined in this document from the German Embassy in Manila. It appears that you cannot make this application while you are in Germany:
In particular, note:
The sponsor must visit the local Registry Office to register the marriage BEFORE the visa application is submitted at the Embassy. The Philippine fiancé(e) does not have to travel to Germany for this.
The visa application must be immediately rejected if it is submitted without this proof of registration
You can get more general information about the process on the appropriate webpage of the diplomatic service. There is a Marriage Visa section with the following links:
You may also be interested in these blog posts outlining the procedure, from Pinays in Germany: