Yo Kass answered
To say 'happy birthday, beautiful friend' in Italian, you could say buon compleanno followed by either bello or bella, depending on the gender of the person in question.
Happy Birthday
The phrase for happy birthday is buon compleanno, with the word compleanno being a compound word meaning something like 'completion-of-year'.
To wish someone a happy birthday, the full form of the phrase is ti auguro un buon compleanno; the ti auguro part is the equivalent of the English 'I wish you, but is not often included - just as English speakers would usually opt for 'happy birthday' over 'I wish you a happy birthday'.
Often, when when wishing someone well on a particular day, the word auguri is sufficient. This is similar to someone saying 'best wishes' in English, and it is usually understood whether you are referring to best wishes for a birthday or to another event, for example New Year's Eve, based on the context.
So, because of this, auguri bello/bella is probably the most common way you'll hear the phrase 'happy birthday' expressed by a native speaker.
Beautiful Friend
Although the Italian word for friend, amico (or amica for a female), would be semantically-correct in its use to say 'beautiful friend', it is conventionally dropped because Italians often refer to their friends with the adjective bella or bello anyway. In fact, including the word amico might even suggest that you wanted to draw particular attention to the physical beauty of your friend.
Happy Birthday
The phrase for happy birthday is buon compleanno, with the word compleanno being a compound word meaning something like 'completion-of-year'.
To wish someone a happy birthday, the full form of the phrase is ti auguro un buon compleanno; the ti auguro part is the equivalent of the English 'I wish you, but is not often included - just as English speakers would usually opt for 'happy birthday' over 'I wish you a happy birthday'.
Often, when when wishing someone well on a particular day, the word auguri is sufficient. This is similar to someone saying 'best wishes' in English, and it is usually understood whether you are referring to best wishes for a birthday or to another event, for example New Year's Eve, based on the context.
So, because of this, auguri bello/bella is probably the most common way you'll hear the phrase 'happy birthday' expressed by a native speaker.
Beautiful Friend
Although the Italian word for friend, amico (or amica for a female), would be semantically-correct in its use to say 'beautiful friend', it is conventionally dropped because Italians often refer to their friends with the adjective bella or bello anyway. In fact, including the word amico might even suggest that you wanted to draw particular attention to the physical beauty of your friend.