A phrase you use in English many times a day is Thank you.
There is 2 ways to say thanks in Cantonese, depending on whether someone is helping you, or whether they are giving you a gift. Note that when you make a purchase in a shop or restaurant, that is considered helping, as you are paying for the good or service.
Thank you. (when someone helps you) 唔該. M̀h’gōi.
Thank you. (when someone gives you a gift) 多謝 Dōjeh.
Mh’goi is the phrase used the most, in day to day transactions.