Woah woah calm down. If you have trouble with english then convert it into Russian.
1 to enter the demon city you must have corruption of at least 15. I don't know which route are you on but go back to the ground, find slimes and submit yourself/lose to them until your COR is 15. Slimes are guaranteed to raise your corruption
2 about the ghosts. Well you cannot hurt them with your sword. You can only use holy fist on them. You can get holy fist by doing witer's nightmare mission which can only be accessed after getting Hakan drunk. If you don't have holy fist then you are in trouble. There are a few sections where you must have to fight ghosts and without your holy fist you can win.