The meaninig is exctly the same in Polish and in English. there are jobs that people refer to as "partners", and there are companies where co-owners are called "partners".
Good point! Law firms have partners and some jobs like the Police have partners as well. But coworkers is a common term in English. Is this correct for Polish? Współpracownik?
Yes, współpracownik is a co-worker. And a partner seems like something more specific, exactly what you wrote about law firms and the police.
It is even wider than this; in Britain there is a department store and supermarket group - John Lewis and Waitrose - whose employees are partners, they have a share of the business and are referred to as partners.
Strange...I saw 'co-worker' as duolingo's translation for this earlier on. I actually wrote it down as it was new to me.