この曲、「僕に彼女ができたんだ」といいますが、タイトルの意味が分かりません。
★ Even though the song is called 「僕に彼女ができたんだ」, I don't know what the title means.
回答は日本語か英語、どちらでもいいです。
Japanese, English - whatever is cool.
This できる means "to come into existence".
「僕{ぼく}に彼女{かのじょ}ができたんだ」 therefore means "I've got a girlfriend now." since it would not be natural to say in English the literal translation version "A girlfriend has come into existence for me."
Note that the subject of that Japanese sentence is 「彼女」 and not 「僕」. Please do not be fooled by the translation: "I've got a girlfriend now.", in which the subject is "I".
More examples:
「今日新しい友だちができた。」
「もうすぐここにラーメン屋ができるらしい。」= "I hear there will be a ramen shop here soon."
「OMG, こどもができちゃった!」= "I/She got pregnant!" I am sure some of you have heard the word 「できちゃった婚{こん}」 or 「できちゃった結婚{けっこん}」 ("shotgun marriage"). It comes from this 「できる」.