I feel a little uneasy

I guess it depends on where you work. In New York, we talk much faster than the people I have met here down South--in the USA. But you also said many of your colleagues are foreigners--foreign to you or your ethnicity but speak English? Make a friend, don't be too nervous. Talk to people, ask questions. If you are funny, jokes always break the ice--don't be afraid to laugh at yourself (or other people because they can be quite amusing ;) ) Some people only wish they knew another language, and if you find the right people, maybe you can help each other out. Ask what things are called if you do not know the word, explain to the fast talkers that you are still learning English and you want to understand them, would you mind saying that again? Or something to the effects, sometimes people speak slower or will break things down when they realize English is not your first language. Be prepared for those that are not so kind, but don't let it hurt your feelings, some people are just mean. Sometimes other people are just unsure of how to attempt communication when they recognize a language "barrier"--some people just aren't teachers. Worst comes to worst, search on Craigslist for an English tutor, maybe you could make a friend or achieve the fluency you desire. Not all English speakers really know how to speak English any way...You'll be just fine.... I understood your entire question just fine, give yourself some credit :)