Notice that George Michael speaks British English but he has an influence from American accent when he sings, especially the way he pronounces the diphthong in PHONE ( /oʊ/ instead of the British /əʊ/ ) and the vowel in SOCK ( / ɑ / instead of the British / ɒ / ), notice the pronunciation of BODY /bɑʀɪ/ , which is completely American (instead of the more British  /bɒdɪ/) . But that’s quite usual in many pop singers: British singers often sound a bit American and many American singers sound a bit British. Maybe because music levels accents or simply because singers want to sound different and special, so they are vulnerable to foreign models. Also affected (to make it sound more sensual) is his pronunciation of faith ( /feɪð/ ), that should be /feɪθ/ .

I GUESS IT WOULD BE NICE= I suppose. In conversational English we often use GUESS with the meaning of SUPPOSE.

IF I COULD TOUCH YOUR BODY= Notice the way he pronounces IF I /ɪvaɪ/ . This is affected pronunciation, not natural, just to sound cool and different. Exactly the same pronunciation of IF can be heard in the Brisith song "Rule the World" or the American song "Wherever you will go".

I GOTTA= This may be the transcription of conversational "I've got a" or (like here) "I've got to".

I GOTTA THINK TWICE= I shouldn’t act impulsively, I have to think about this carefully before taking a decision.

GIVE AWAY= If you give something away you just give it for free. If you give your heart away, you are so much in love with someone that they are the owner of your heart and emotions.

I KNOW ALL THE GAMES YOU PLAY= In social relationships, to play games means to have strategies where you try to get things from people by acting in a dishonest way. So if you play a game with someone, you are deceiving them.

TIME OFF= If you have some time off from a situation you go away and have a rest, usually to think about it or recharge your energies.

PICK UP= If you pick something up, you lift it from the ground.

OFF THE FLOOR= The particle OFF expresses an idea of separation, so if he picks his heart up OFF the floor, it simply means that his heart was on the floor ( it was thrown away, without value, like litter) and he lifts it from there to a more honourable position. That means he wants to recover his dignity and be an honest valuable person again.

DEVOTION= The act of devoting. To devote is to give your time, attention or energy to a person or activity.

WHEN THAT LOVE COMES DOWN WITHOUT DEVOTION= Here he is criticizing the kind of love she used to give him. When love comes without devotion it is empty, a fake, because true love is not just feeling for the other but, to some extend, living for the other, devoting part of your time and energy to the person you love.

IT TAKES A STRONG MAN, BABY, BUT I’M SHOWING YOU THE DOOR= Baby, to do that a man has to be strong. He says that rejecting her (showing her the door) is very difficult, only a strong man can do it. But he is strong and is telling her to go.

‘CAUSE= Because.

I GOTTA= I’ve got to, I must.

I GOTTA HAVE FAITH= I must have faith in love, and believe that I can find something much better and authentic than the empty love you offer me.

THE BLUES= If you are blue or have the blues, you are sad. If you give someone the blues, you make them sad.

YOU MEAN EVERY WORD YOU SAY= If you mean what you say, you are serious about it, you’re not joking.

CAN’T HELP BUT THINK...= If you can’t help doing something or you can’t help but do something, you do it because it’s impossible for you not to do it, you have no alternative.

THINK OF YESTERDAY= Remember that the verb THINK uses the preposition OF or ABOUT.

TIED ME DOWN= If something ties you down (or ties you up) you can’t move because you are tied or, metaphorically, because you have no options to choose.

LOVERBOY= This is how girls sometimes call their boyfriends: "come here loverboy". In this song it is used with the same meaning as "lover".

LOVERBOY RULES= In the beginning he said that they were both playing games with each other. The rules of the game are the "loverboy rules", that is, the rules that a lover must follow to play the game of seduction and fake love.

BEFORE THIS RIVER BECOMES AN OCEAN= Before this emotion that is beginning to grow is so big that I can’t control it. She is really tempting him, he doesn’t want to go back to her because now he wants to find true love, but he feels lonely and when she tries to seduce him back he begins to feel something for her again. But he must stop before it’s too late and reject her again.

BEFORE YOU THROW MY HEART BACK ON THE FLOOR= Remember that his heart was on the floor because that relationship had degraded him, so if he goes back to her his heart will go back to the floor.

RECONSIDER= Think about something again, especially with the intention of changing your previous decision.

FOOLISH= Silly, stupid.

HOLD ME= Embrace me, hug me, put your arms around me.

I’LL WAIT FOR SOMETHING MORE= I’ll wait for something better. In this sentence he uses WILL because he is taking this decision at this very moment. So the end of the song is the end of his doubts. Now he has firmly decided to leave her and look for something better. No more doubts about it.