and do I have to give copies of my diplomas to the company who is going to apply for WP for me. Because i find it strange that they required only a copy of my passport in order to apply for Work Permit.
To give you work permit employer has to prove that he cannot find proper candidate from Poland, not that you have diplomas. It would be different if you had Polish diploma - then you could work without work permit.
As I can stay legally in Poland holding the Student residency card from EU country.
Study that: ec.europa.eu/immigration/tab1.do?subSec=30#move
And that: migrant.info.pl/Work_permit.html
Who requires a work permit in Poland?
A foreigner who is not an EU member states national is entitled to perform work in the Republic of Poland on the basis of a work permit if he/she legally resides in Poland on the basis of:
a visa (exceptions to this principle apply- they are available here -> );
a Schengen visa or another residence document issued by another Schengen area member state;
a residence permit for a fixed period (exceptions to his principle apply and are listed below);
on the basis of visa-less travel if the provisions of an agreement concerning visa-less travel foresee the performance of work by foreigners (nationals of which counties can enter the Polish territory under the visa-less travel arrangements?->).
So it seems that your student residency card is enough to apply for work permit in Poland if it doesn't expire.