How long would it take me to loose 25 pounds off my body?

Well im about 5' 7" 22 years old male and ready to go on my 4 week vacation and i recently weighted my self on the bathroom scale and i weight 204lbs! i remember that i use to weight 179lbs. Mostly i want to target belly fat but then my over all weight but i don't know where to start on my exercises. I already changed my diet to a better one but i don't know what exercises to do. Is their any tips that anyone can give me on any help full exercises? What kind of exercises should i do a day, the duration and how many times a week should be help full. If i keep up my exercise schedule great in how long would i be able to see results? Im planing on keeping exercising after my 4 weeks of vacation either way. Also, is their anything i should take to help me out like any kind of tea, shake, pills? Anything i can buy at a gnc or target or walmart??. Thank you!!