My problem solved some how.
I delete everything in the game folder.
I reinstalled the game again.
I had backup of "Saves" folder.
I start a save game before getting any quests related to Mission.
Then, Mission appeared again in Under City.
I think that starting a new game is the best solution as you say.
I played another game. Maybe you know, Skyrim. Most of the mods' installation instruction, they say "make a clean save". It means, create a save with your main mods/patches at Level 1 before the mod has been selected. Then, you can start the game from "the clean save" with the new mod after you selected it first.
I think, it's the same principle.
I still have texture problem from time to time. I partially get black floor outside of Dantooine on Matale and or Sandral Grounds.
It appears just on a small part of the full texture. Maybe, quick start can solve the problem, or totally quitting and restarting the game is better option.
Thank you for your help.
Cheers...