About Poland's visa extension

Hello,

So I recently applied to extend my stay for 4 more days which ends tomorrow but I'm still in the 7 days period which finishes on Monday about supplying the additional documents and making payment, I have the stamp on my passport that I have an application undergoing, is it fine to stay until next week since I still don't have any news or decision about my extension application?

As long as you formally / legally applied for your visa extension and you await their response, I'd assume it is ok to legally stay in Poland. A similar situation was during the Covid months where people applied for extensions and haven't received a reply for months. But it turned out it was acceptable.