How to Extend a Schengen Visa while being within Schengen Area?
Generally, a person can only apply for a visa extension if they can provide compelling reasons for why they need to extend their stay.
SCHENGEN VISA VALIDITY vs. APPROVED DURATION OF STAY: KNOW THE DIFFERENCE
There are two essential aspects of a Schengen Visa that one needs to consider: the validity of the visa and the approved duration of stay.