I do not have experience in "live" translations. Native Polish speaker... "rusty" spoken (not many occasions to actual voice it) English based on spending several years in USA, very very very long time ago, maintained by reading internet and some listening like yt or pirate movies..)-; consider only if you do not have any other alternative. and lastly, as you can see, I'm not from Warsaw... would require additional overnight lodging... or I could try bothering my distant family there... anywayz, all those people you mention should be speaking perfect lingua franca, not?