Weight on legs and backside

You'll need to be in an overall calorie deficit. You can target certain muscle to build and strengthen but you cannot pick specific body parts/areas from which to lose fat. When you lose fat, it's from all over the body. Additionally, since most of us have more fat than we think we do and it's often in spots we don't think about, you have to be very patient and think long term when it comes to losing it.