How do I abandon a quest
To abandon a quest, open your Quest Log ("L" by default) and click on the quest you wish to abandon. Then you want to return to the NPC that gave you the quest. If the quest is a part of a quest line, you would return to the last NPC that you interacted with. If you get a duplicate item error, delete the item that was given to you when you accepted the quest initially.
Please note that if you abandon a quest, any quest items you have collected for that quest will be deleted.