I get a quest to kill/fetch something and I simply do not find person/thing.

More often than not I end up searching every square inch of the dungeon and never find my target.

You can always use the [] to teleport between quest locations in a dungeon as a last resort.

im sorry I dont understand?

Use the keys that make those symbols to cycle through them. (That is assuming you have the cheats activated in the config file.)

Pressing either bracket keys on your keybord [ or ] teleports your character to one of the possible locations where your quest item/enemy/NPC is. If you really can't find something in the dungeons, use these keys.

I've done that for a while as a last resort, but there are occasionally times when even doing that still does not take me to the quest target. I've failed many a quest because of this problem.

It's possible you suffer from the invisible quest item bug. It's quite common if you don't play the game in DOSBox.