就算我在怎努力也只是曾经
[jiù suàn wŏ zài zĕn nŭ lì yĕ zhĭ shì céng jīng]
It roughly translates to 'No matter how hard I try now, it’s still only part of the past.' It conveys a sense of nostalgia, helplessness, or regret, perhaps about lost opportunities in love or friendship.