Although in St Petersburg a lot of people speak at least basic English, it is always useful to be able to say something in Russian. It can help you if you come across someone who does not know a word of English, and also it will please the locals who will see that you actually took some effort to learn their language.
Good day – Dobry den (same as “hello”)
Hi – Privyet (informal)
Yes – Da
No – Nyet
Thank you – Spaseeba
Bye – Da svidanya
How much? – Skolka stoit?
Too expensive – Slishkam doraga
Good – Kharasho
Where’s the toilet? – Gdye tooalyet?
Help! – Pamagitye!
I don’t speak Russian – Ya ni gavaryu pa russki
I don’t understand – Ya ni panimayu
I am the happiest person ever, as I finally made it to Russia and now enjoying beautiful St Petersburg – Ya samiy shchisliviy chilavyek patamushta ya nakanyets priyekhal v Rassiyu i naslazhdayus prekrasnym Peterburgom (this last one is a joke, but try to say it anyway)
If you learn these phrases, they might be of great help in Russia. And if you spend a couple of weeks in St Petersburg, you will be fluent!