How do you manage to study and have a balance in your life at the same time?
Yes, it matters that you are in grade 9. It is probably a good thing that you are able to do what you like to do (math and computing), but it seems too early to focus yourself quite so much on narrow interests. The problem that might arise is that you get burned out before you are 20 years old with no backup plan for your life and also poor health and no relationships with people. That would be sad. 

It is good to work intensely at something, but not quite as good to do so to the exclusion of other things. There is a lot to learn, and you are recognizing that now, at least a bit. In fact, making time for those other things, such as exercise (aerobic especially) and relaxation (reading, talking, ...) can actually make the intense study that you do more effective. At least this is true for most people, though there are exception. But, for most, continuing to push hard against an intellectual problem, say in math, can just waste time and lead to a deeper block, than taking a break. It turns out that, again, for most people, the brain/mind will continue to work on putting connections together when you are engaged in other activities, even sleeping. 

But, for someone as young as yourself, I'd suggest that you think about the following priorities. First, your health, both mental and physical. Next, your relationships, both family and friends. Next, getting a lot of experience of different kinds, studying lots of things with deep study of a few of them. You seem to have the deep study part mastered, but may be missing out on the wide experience that can make the deep study more meaningful and also give you options to change direction as you grow older. 

It is good to have some direction in your life, but not, yet, a good idea to exclude all other potential paths that you might follow. 

As for time management, you can do it formally, or informally. If you joint a sports team or other directed activity, then your schedule will be set for you. But you can also just decide that you will ride your bike for an hour every day - preferably with a few friends. Or you can just decide, even more informally, that when you get stuck on a math problem that you take a walk in the woods for half an hour, or read a chapter in a book. Something to provide a bit of variety. 

At a later stage in your life you will be forced by circumstances to specialize in something. It is good if you put that off for a while so that you have the opportunity to make the decision about where to specialize with more background knowledge and experience than you now have.