How can I fix this dental problem?

Well first of all, if you still have your baby teeth, maybe you could wait out on fixing your teeth. Once you have your adult teeth, then its worth it to invest on whitening solutions. As for the gaps, you could go to an orthodontist and get braces or invisalign trays. But sometimes, gaps aren't fixable and you'll just have to deal with it. For now, I suggest brushing and flossing atleast twice a day , using mouthwash and a tongue scraper to freshen your breath, and a whitening toothpaste if you'd like.