Answer by
HuiMin (25)
Congratulations, in general is 恭喜 (Gongxi) or 恭喜你. If it's a wedding, write/say 百年好和 (Buy nian how her) or 白头偕老 (Buy toe xie lao), both of which means that you wish the marriage will last a lifetime. For birthdays, write/say 生日快乐 (sheng re kuai ler), which just means happy birthday.