Hi, feel free to say "Hello", Andre! A friend used to be a stranger! Back to how to express greetings, it depends on the context, age, and every culture! Example, in the UK we often make acquaintance by talking about the weather, " Hello, is it a lovely day?", "Good morning,do you hear the weather forecast today?" Or another example,if you meet a Vietnamese,they will say hello, or ask about your age, career, how do you feel about something,... etc to creat a friendly topic! Every culture has its own ways, but actually we all will introduce about ourselves (name, nationality, hobby,.... etc ) or ask our partner for their health, a problem that everyone is talking about,... etc