I honestly don't know what fat you're trying to lose on your stomach. You pretty much have no pooch. That little bit that sticks out is natural in everyone. The only way you can get rid of that is to either suck your gut in or flex your stomach muscles. If you look at a side profile of a human skeletong the ribs stick out further than the breast bone (don't know the scientific term). That little pooch is where you organs, such as your intestines, rest, so don't worry if you stand up straight and relaxed if the side profile of your torso, sans your boobs, is not completely vertical. What you see in magazines and pictures is people flexing or sucking in their gut (or are digitally altered). I'm just telling you this in case you think your stomach should be flat as in its completely vertical as I really don't see what pooch you're referring to.
As for your butt, well, I'm gonna be frank: it's enormous. It's very big. You've got the Hispanic thing going so that's probably why. I don't know how you would lift your butt or even what it would look like if it were lifted honestly. It seems pretty round already so I don't know what to say. If you've got a little cottage cheese thing going on (which I doubt but I could be wrong) then, yes, you'll want to lose some fat. I'm no personal trainer or anything but in my experience in observing women's asses, I've never seen any of them INCREASE in size by burning fat. I've seen it get bigger with muslce gain though. You want to keep it the same shape but make it firmer though, right? Well, for that, listen to the other people's suggestions but you really can't just lose fat in only certain areas, so if your stomach gets smaller your butt might. This is just speculation though. Again, I'm no expert.
One thing I'm surprised no one has suggested here is doing exercises that focuses directly on your butt muscles. Specifically, things like where you tie one of those stretchy things (don't know the term but they're made of rubber and have handles at each end) to something near the floor, put it around your ankle and, facing towards the stretchy thing, keeping your leg straight (locked), kick your foot out behind you.
There are similar exercises you can do as well that'll work both ass muslces. One is one those pieces of equipment that you can do inverted sit-ups on (yeah, I really don't know the names of these things), that thing where you brace your feet against the feet pads, face down on your stomach and bend your back and bring it up like a cruncher only facing towards the floor, well, do those but KEEP YOUR LEGS AND FEET TOGETHER AS CLOSE AS YOU CAN AND KEEP YOUR KNEES LOCKED. I capitalized that because doing them this way will work your butt muscles a lot. The way I've seen a lot of people do these is they keep their feet more apart and bend their knees. Bending your knees on these will take all the strain off your butt and that's not what you want.
Another very similar thing is done on a pommel horse. Most gyms don't have these (unless you're at a school gym maybe--or a gymnastics gym of course) so the next best thing would be to find some sort of high bench, but really I haven't found anything like that myself. (That's why I do what I mentioned in the above paragraph.) I like these because they're very precise in working these muscles. What you do is you face down on the horse/bench with your waste hanging off the edge so only your stomach and chest are touching the top of it. Grab underneath and then swing your legs up as high as you can, again, keeping the feet together and the knees straight. To the degree you bend your legs or move them apart, you'll defeat the purpose of exercising the ass muscles proportionately. In other words, don't cheat at all, even if you can't go that high (which you probably won't). You can vary it a little by starting and going no lower than 45 degrees or even horizontal. You should really feel it and your ass will probably be sore afterwards.
That's one thing about gymnasts: since they swing backwards a lot of times their butts are very strong because they need to squeeze them to do this. Watch the girls in the uneven bars or the men on rings if you want to see what I mean. Those guys could probably crush cans in their cheeks.
I don't know how strong or firm my butt is but I can feel the muscles there really being worked by doing this. Try it out.