Ukrainian is the official state language of Ukraine. However, Russian is widely used throughout Ukraine, especially in eastern Ukraine. You may find that people in cities of western Ukraine may only speak Ukrainian. Your translator and/or facilitator should take care of all of your translating needs. But there may be times when you might need to speak to a Ukrainian without your translator.
Ask them “English” and see if you can communicate to some degree. Some Ukrainians may also know other European languages, like German. Every year, the number of English speakers grows substantially, but knowing a few useful Ukrainian words could be very helpful. The following list are commonly used Ukrainian words and phrases:
dobriy dehn – hello, good day
dya-koo-you – thank you
bood laska – please / you’re welcome
spa-see-ba – thank you
skolka – How much?
schtor – What?