I'm doing it right now have lost 4 kg in a week and its cabbage,cauliflower carrot and peepper soup is it healthy to drink it

Not every day for weeks, if you are doing that silly fad cabbage soup diet. It is OK to do at times. The issue is if done too long you will merely gain the weight right back plus after a point it is not a healthy weight loss. Only by doing a balanced diet and adding enough exercise will you do proper weight loss.