Eating some soup can help you lose some weight in a week but not a whole lot of weight will be lost by just eating soup and certainly not only in a week.
Eating soup that is low in calories can help you lose weight but it can take more than a week to see significant weight loss from just eating soup.
If you want to really lose weight by eating soup then you should also get out and exercise, ride an exercise bike, treadmill etc.
Even go hiking, jogging, kayaking etc can help you lose weight and you'll lose a bit more weight in a week by being active, exercising etc than you would with just eating soup.
However losing significant amounts of weight can take 6 months to a year.
Losing too much weight too fast can be unhealthy so take it slow and overtime you should lose the weight.