Hello i am styding mandarin 2 years now and i have some suggestions for you
say hello
您好 nín hâo nin is the formal YOU
before nin hao you can add "sir" or "madamme"
先生,您好 xiānsheng ,nín hâo = hello sir
小姐,您好 xiâojie , nín hâo = hello lady , madamme
You can also use the time expressions
早上好 zâoshang hâo goodmorning from 7-10
上午好 shàngwû hâo goodmorning from 10-12
中午好 zhōngwû hâo goodevening from 12-1:00
下午好 Xiàwû hâo goodevening from 1:00-19:00
晚上好 wánshang hâo from 19:00-.......
to close a conversation you can just say
再见 zài jiàn cu soon it is as formal as informal
oher expressions...
好久不见 hâo jiû bù jiàn long time to see you
可以..... Kê yî could i........
我想. ........ Wô xiâng..... I would like.....
不客气 / 没关系 búkèqī / méiguânxī as an answer to thank you ( you are welcome)
谢谢 xièxiè ( thank you)
Hope i helped
1. 诸位女士诸位先生... means ladies and gentleman
i suggest some of words for starting:
1.大家早上好,我很荣幸在这里能见到你们。(Hello everyone,good morning,i'm glad to see you here today)
2.女士们先生们,早上好,我叫。。。。欢迎你们来到这听我的演讲。(Ladies and gentleman,good morning,my name is...welcome to come to here today to listen me presentation)
Hope that help you~