Hello, I thought a few helpful tips might clear up some problems you are having with quests.
1. It is not wise to have many quests at one time, the more you have, the more likely you will get problems. HOW? You have to go to other NPCs in most quests, so chances are you will need to go to 1 NPC for 2 or more quest reasons. So when you talk to a NPC in quest terms, they will only respond to the first quest you have.
2. Lost quest item, sorry no other way but to log an alto, [Alto refers to other characters on your account] Get the item you need from doing quest, then either give to a friend or hide for your main character to pick up.
3. If you are asked to say yes or no, but you get do not understand type message, go back a step and try something slightly different, for example first time you say "green apple", you get follow on quest text. then asked to say yes/no. do not understand. Now say "little green apple" or "apple" Hopefully now the quest will work.
4. Now other way round, you are asked; do you know..... ?. You say "yes" no reply or do not understand. In this case answer the question, do not say "yes". [General rule here is if asked a leading question; give answer].
5. Some quests, just for no reason, stop or you get nowhere, in this case go back to last NPC or even further, to pick quest up again.
6. We are all prone to type words wrong, so please make sure you spelt it right, and believe it or not Very rarely a typo might creep into the NPC text.