Working at an Aussie cafe

Hi im in high school right now and i speak Japanese as my first language and English as maybe a second language. But i think my English is up to a level were i sound like a native and people usually think im probably fluent in English. Its been my second time working in a cafe but its my first time in Australia and im so scared to talk to customers. Not like im scared of people but they’re fluency in English which i thought i had no problem to handle with and casual talk is not really my thing. My accent gets weird around those English speakers and i sound so dumb. The strong energy they give doesn’t match me. Even tho i look Australian and i know my English isn’t bad, when im around customers i just feel so weak in speaking English. Not being racist but whenever the customer is asian, i feel comfortable and able to communicate well. How do i get used to casual talk and taking orders from customers(especially English natives)without feeling scared or nervous. (Sorry my grammar is weird)