i have completed main story but i only cleared the dungion of water sprit and those i dont have cleared now i have a new qwest chance but i dont know. What to do it says that i have to go lag... In dragonia but when i go its says prepaire and .....

If you have the quest "Last Chance," it means that you've finished the current main story. You can go around and do other things, but the main story can't be advanced any further yet.
There are a few optional riddle dungeons during the main story. You can still go there to solve them, but they weren't needed to advance the main story.