Second, if you want to feel more intimate, you can call people older than yourself "elder brother" or "elder sister", but if you are in your twenties and meet people who are obviously in their fifties and sixties, you should not call them "elder brother" or "elder sister" but "uncle".
Third, don't call people younger than yourself "brother" or "sister", you can directly call them "Mr. X" or "Ms. X";
Fourth, women with uncertain grades can be called "Ms. X" in a unified way. If they think they are students, they can be called "classmate X". If they think they are young and unmarried, they can call them "Miss X" (the word "Miss" is derogatory, so it is better not to use it).
All of the above are aimed at customers or strangers. If you are a colleague, you usually address yourself by name+title, such as "Manager Wang" and "Zhao Zong". If you are a colleague, you can call it whatever you want. It's not impossible to call them by their first names. If you have a good relationship, you can call them "Lao Zhang" and "Yuan Yuan" at will.