exercising and eating right will definetely improve your concentration. Good job at starting to work out. it can develop into a life changing experience even starting at the most basic level, like lifting your bass amp. lol. I played bass for a long time and yes they are pretty heavy. Is the dance routine a class you are taking or are you just dancing around like crazy on your own? dancing is a great cardio workout provided it is intense. For your diet, stick with healthy fats, complex carbs, and protein. these will all help. eat lots of fruits and vegetables, and if your not already, start taking a multi vitamin. im pretty sure i have an undiagnosed case of ADD but ever since i started eating right, working out, and taking a multivitamin my concentration has definitely improved. Make sure to eat breakfast and drink lots of water. If you are a coffee drinker like me, eat before your coffee and have at least one bottle or glass of water before you start drinking the coffee. this will give you solid food energy, and hydration to start your day off right.
I know you may not have a lot of time to get to the gym but you only need about 30 to 45 minutes of exercise about three times a week to start. I have read about some good routines and they are all whole body routines that can even be done from home which makes them ten times easier. You are going to have to build your muscles in order to lose weight effectively. all of your muscles. you do not have to do body builder lifts or anything like that, but when your body is recovering from lifting it is burning fat. so insead of your body burning fat during just your exercise it is doing it while you rest as well. mixed with the right amount of cardio it is a solid plan to get you started.
you are starting off right by exercising with the means you have. the best thing you can do is just get started no matter how small. hope this helps. if you have more questions, just ask. good luck.