What a beautiful song ! As so often, the most famous English version doesn't convey the power of the song. Jacques Brel's phrasing is unconventional, so the lines compress and run over, and the tempo hesitates and speeds up. It feels like conversation, more human and sincere. Sing this in a more formal or "English" way and much of the inner poetry is lost. The inner pulse is 5 syllables around which the words wrap. (Please also see my post on Gloomy Sunday, Song with a Curse)
Here's my attempt at translation, which is tricky as so much of the original depends on allitration and word play. "Don't leave me. It would mean forgetting everything, everything that can be forgotten, which has already flown away. Forget the times of misunderstanding, and le temps.... perdu. How? to forget hours the hours whose memory can kill, sometimes, with the blow of why? The heart of happiness."
"Me ! I could offer you pearls of raindrops from distant lands where it never rains. I'd dig the earth, even after I die, to cover your body with gold and light. I'd create a realm where love would be king, and love would be law and you would be queen."
"I'd invent for you crazy words that you would understand. I'd speak to you then of lovers who've twice seen their hearts embrace. I'd tell you the story of this dead king who was not able to meet you again. Don't leave me."
"One has often seen regenerated, flames of ancient volcanos which seemed too old. It could be that scorched earth gives more wheat than a good April. And when evening comes, in a blazing sunset, don't red and black combine?"
"Don't leave me. I can no longer cry. I can no longer speak. I'll hide myself away where I can watch you dancing and smiling. I'll listen to you sing and laugh Let me become the shadow of your shadow, the shadow of your hand, the shadow of your dog"
The girlfriend, like millions of women before and since, will recognize this type of man. "It's all about you, you, you", Who gives a stuff about promises when the guy doesn't deliver ? But it's still such a moving song, especially the way Brel sings it.