"Happy birthday, my girl" is the Engpsh translation for "生日快乐，我的女孩" in Chinese. The phrase "happy birthday" is a common and traditional phrase used to wish someone a happy birthday on their special day. "My girl" is a term of endearment used to refer to a significant other or a close female friend.

Here are some examples of how you can use this phrase in a sentence:

"Happy birthday, my girl! I hope you have a great day today."
"Wishing you all the best on your special day, my girl. Happy birthday!"
"Happy birthday to the most amazing girl I know. Love you always, my girl."

Note that, "girl" can be replaced by "lady" or "sweetie" or "dear" and so on, depending on the level of intimacy with the person you are wishing birthday.