I'm planning to change my job now and move to new company ,, so do i have to apply for totally new karta pobytu?
I would suggest you to call the voivodeship that you plan to move in case you are changing your city along with your job.
In your case, if you are not changing your city - first you should notice foreign office that you have your residence permit decision from , after - you leave your job.
And then you have 30 days to find a new job, in that 30 days you need to provide them the new contract otherwise after 30th day, you need to leave the country.
So in this case, you just need to provide them new job contracy.
If you are changing your city, you should go to the foreign office in the city that you plan to move. you should give them your new address registration and new job contract stating them that you have your residence card in connection with your graduation.