If you want to stay longer in Australia, you will need to submit a new visa application.
However, if you have an 8503 ‘No further stay’ condition on your visa, you cannot apply for a new visa while you are in Australia. You must leave Australia no later than the date of your visa expiration, except in extremely limited circumstances.
Our expert migration consultant at MSA Immigration Australia can help you with applying for visa ‘extension’ or request for waiver of 8503 ‘No further stay’ condition.