I was watching a film named "500 days of Summer" and at the end there was a song starting like "She's got you high & you don't even know yet". Since I'm not a native speaker, I don't understand what does it mean? I need some help.
"High" can be used to a refer to a mental state, usually a euphoric one. This can be used to refer to an induced state of euphoria from drugs, but it is also used to describe other natural states of happiness (eg "I'm on a high").
"She's got you high and you don't even know yet"
It is impossible for anyone but the songwriter to say authoritatively what the song lyrics mean, but it seems to me that the song is about someone in relationship with a girl who is making them very happy. The girl may love the person, or they may even be in love but either the person doesn't realise it or is in denial.
"She's got you high" means that the unnamed girl has made the person euphorically happy, maybe that they are even in love; and "You don't even know yet" implies that the person has not yet realised they may be in love, or perhaps just what a good thing this relationship is.
Other lyrics from the song that support this interpretation:
You can't deny you're looking for the sunset
Perhaps this means metaphorically that the person is looking for something beautiful? Again there is a suggestion of being in denial.
It's the search for the time before it leaves without you
Suggesting that if the person doesn't realise this girl is a good thing and respond, she will move on.
What's this about? I figured love would shine through
The writer is saying that love should be obvious, but the person hasn't realised it.
Open your mind, believe it's going to come to
Telling the person in the song that they may be in denial that love will ever come their way, but that this is "closed minded" thinking.
She has put you in a euphoric or inebriated mental state, a state where your judgment may be impaired, and so far you are unaware that this has happened.
I don't know that song, so it's impossible for me to say whether the singer or lyricist thinks this fact is good news or bad news, happy or sad, funny or tragic, a lighthearted jibe or a serious warning.
The question is what is it that "You don't even know yet?" It's that Summer does not love you, will never love you. As a character in a movie once said, "I didn't know that only one person could fall in love - I thought it was always two people." (I can't remember the movie, just that line.) And at the end, when he tries to start up a relationship with "Autumn," he drops out of character to seemingly ask, "Am I going through this again?"