Thou is correct in part this is how it works, the underworld of Hades is were most go whom die in their sins and whom most will go whom has lived on earth, the valley of the dead siteth before it and mankind calls it earth. Each shall spend a time in underworlds of Hades according to what they have sow, but for some whom have done greater evils they shall fall also into the lake of fire. Now do not underestimate the suffering that occurs in both these places it is hell but it is not the greatest of Hell and is a temporary imprisonment. The suffering on earth can not compare to the suffering in underworld but yet again nor can suffering of lake of fire compare to suffering of underworld, but greatest suffering is known as the Outer Darkness which cometh by the second death. The underworld and lake of fire in time they can be released due to atonement but the outer darkness once taken is forever the atonement does not apply, the outer darkness is beyond even the comprehension of Hades and is their final resting place as a consequence to continuously choosing evil without repentance.

So indeed some of hell is temporary and the greater of Hell at final judgement is forever, but few will enter that one for it is not Gods will all are lost forever even murders can be forgiven in eons. If thou spent one second in even underworld you would be terrified and in great pain. Do all you can to avoid falling beyond the land of the dead.