"I miss you already, my dear."
Let's break it down:
* Tu: You
* you: (This is a grammatical error in French, it should be "me" or "manques")
* manques: miss (verb conjugated in the present tense)
* déjà: already
* ma: my
* chérie: darling, sweetheart
It's a very sweet and romantic phrase, often used by someone who is deeply in love and missing their partner.