What a cute frog! Thanks for sharing!
Those fruit flies might be fungus gnats that appear when there is fungi, algae, and/or plant roots in the soil. Only the larvae eat, the adult gnats are harmless but can get annoying in large quantity. Make sure to check your substrate regularly for any signs of fungi or algae. At the first sign of any of these, change the substrate completely. I've seen these guys come from the moss covering the dirt of my house plants where they kept the soil under always moist. I stopped using moss completely after that. Also check around your home for any pots, plants, food, water, walls (under sinks, in bathrooms, any place that may store a lot of humidity and moisture. If on walls, call a professional to help as that is a serious health risk) that may have mold, fungi, or algae as this would just bring more flies that can get into your frog's habitat. It would also help to research what species of fly it is to determine how they come about and how to get rid of them.
Hope this helps!