The quest with grey does not work when I go to the blacksmith to make the katana pops up this error
Since that doesn't seem to be a wide spread issue, I assume something is wrong with your files. Maybe try to re-download the full game to ensure you have everything. You can still continue your saves. On Android re-installing the game via the .apk file will update the game without touching your saves, and on other systems you can copy the content of the www/save folder of the old game to the same location of the new game folder.