how to say: "I go here first, then there, right?" wǒ xiān qù zhèli zài nàli. duì ma? (I'm asking which delivery to make first at a restaurant)

Best word to refer to a customer at a restaurant? 客户or顾客? I need to be able to call for the owner whenever a customer is at the restaurant but I'm not sure which to use.

Working at a Chinese restaurant as delivery, what sort of things should I learn to say? (and hear) Hello, I just started working as a delivery driver for a local Chinese place here. My tones are fine, and they understand me when I do say a word or two in Chinese to help them understand something. But, I literally only know a few words and grammar, so what should I do to start speaking with them USEFULLY right away? (One thing specifically I'm looking for is how to say 'I'm off' or something whenever I get a delivery, I feel like zai jian is not appropriate.) In Japanese, I always talked about hobbies and such, but here it's a little more unclear since it's a work environment. I wait for a delivery, go up, they explain to me the address, and I tell them if I understand or not, then I go. I'd like to be able to help them with misunderstandings with English, like they didn't understand "no breading" and I looked up the word for bread and said it to them and they understood. I'd like to be able to do this with out looking up words, but how do I know what to expect? Thanks!