Using Chickytutor.com to simulate a 'chai-shop' conversation for my upcoming trip to Kolkata

I’m heading to West Bengal in two months for a wedding. I’m fine with memorized phrases, but I’m terrified of the actual conversational flow. I’ve started using Chickytutor.com to simulate ordering tea and navigating transit so I can build some listening confidence before I land. Should I focus more on formal vocabulary or are there specific 'street' colloquialisms that will make me sound less like a tourist? I am asking specifically about learning Bengali, not a generic study routine.