To learn more on legalization of your stay, please, have a look at the links below as all the details are clearly explained there:
https://en.migrant.wsc.mazowieckie.pl/
https://en.migrant.wsc.mazowieckie.pl/procedure/Stay
https://en.migrant.wsc.mazowieckie.pl/procedure/EU-citizens
and contact:
Mazovian Voivodship Office in Warsaw
Foreigners Affairs Department