From the time of submission of your application, your temporary residence permit will be issued within some days. Under your temporary residence permit certificate, you can stay in the country as long as you wish.
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How long can I stay in Greece while waiting for temporary residence?
How long can I stay in Greece after applying for a temporary residence permit as a non-EU citizen? Is it better to apply for a national type D visa that will allow me to stay in Greece for a year while my residence permit is being processed?