I need to lose some weight?

i need to some weight, one bcuz im havin a pool party in two weeks, two i weight as much as ma mom, three i dont like ma stomach, four ma boi weights less than me P.S. im only thirteen also i was told if u do sit ups for two weeks u will get a six pack iz this tru if u can giv me some dieting advice and work out advice that will sho results in at least two weeks plz thank u o yeah im a gurl