Walking's ok, but you're better off doing some weight training or cardio - walking doesn't raise your heartbeat much. In general, 30 minutes of cardio a day would be better than 2 hours of walking.

You can lose about 20 pounds in two months so yes

but walking is not enough.

Run ! And do musculation

where you arent big it is going to take you more to lose weight.

you have to work harder for your goal. So you will need to exercise more. Do some cardio like running to get your heart rate up

You will probably lose that weight before summer is over