Why do people think that non-believers are gonna burn in hell forever? when the BIBLE CLEARLY STATES.....?

Malachi 4:1, 3 The day cometh, that shall burn as an oven; ... and all that do wickedly, shall be stubble: and the day that cometh shall burn them up. ... And ye shall tread down the wicked; for they shall be ashes under the soles of your feet. "DOES BURN THEM UP" AND "ASHES" SOUND LIKE IT IS EVEN GONNA TAKE VERY LONG? I think God is gonna make it as quick as possible He is a God of Mercy. He cant force people to come into the kingdom if they want to jump in the fire and commit suicide that. is their choice. and i am talking about people here not the false prophet or Satan. and if the wicked people are gonna burn forever that would mean they would have eternal bodies like ours. But they definitely wont.