32:5 He governs all that exists, from the celestial Highs to the Lows. And all things evolve higher to what they are meant to be in such stages where a single Day before Him equals a thousand years according to your count. [22:47, 35:10. And some of these stages span fifty thousand years each, of your count. 70:4]
Time is relative.
Think of the Quran as a Book for planet earth, with man as its recipient who should read, understand and implement the humanitarian teachings within. When enough human beings get together with this objective they will achieve a paradise on earth, which is described as a ‘hidden garden’, jannah, because it is not at present in front of our faces. We should have faith that this will happen and work hard to bring it into reality. Our efforts now will be painful, full of setbacks, but the inevitable will happen provided we keep working.
Throughout the process we will still see people creating a hell for themselves and others; they will achieve nothing now and in the future. How can they get a future paradise if they are creating a hell now?
As regards life after death, leave that to Allah. He will decide who were genuine and reward them and who are going to lose out.
Why does the Quran use the fire metaphor for hell?
Because you can create anything you want but when fire consumes it, ashes only remain! Your wrong efforts lead to nothing. Similarly, boiling water is also used in the Quran: normal temperature water nourishes plants and animals, hot water destroys them. When we do something we should make sure it is right, or else the inevitable happens!