More and more people speak English in Ukraine, many services in big cities have staff who can speak at least some English, but it is always better to have a personal interpreter (who will be also your personal assistant) so you can avoid any misunderstanding or if you go to a smaller town.
If you are invited to a family’s house bring a small present for the hosts (sweets, flowers, a bottle of wine and a small toy for a kid of any). If you choose flowers make sure it is an uneven number of flowers and do not give knives, clocks/watch, and handkerchiefs – some Ukrainians are very superstitious.
Be ready to take off your street shoes when entering the house. Usually, you will be offered a pair of slippers (“tapochki”).
Be ready to make a toast to the host’s health during the diner.
In Orthodox churches, women cover their heads with scarves or hats, but men take off their hats.