What is a work partner? Maybe coworker would be less weird?
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.
So "I have a new workmate" is wrong as well?
Yeah, let's keep partner a partner.
"I have a new job parter" - nie?
Strange...I saw 'co-worker' as duolingo's translation for this earlier on. I actually wrote it down as it was new to me.
Maybe you have seen "kolega z pracy".