Traveling to Zadar next month; how much do I actually need to know about verb aspect?

I’m visiting Croatia in four weeks and I’m worried about the imperfective vs. perfective verbs. I feel like if I use the wrong one, I’ll sound completely unintelligible while trying to order coffee or ask for directions. Should I put my energy into perfecting aspect now, or should I focus on basic phrases and hope the context carries me? I am asking specifically about learning Croatian, not a generic study routine.