Advice for a student getting back into fitness?

Hi everyone! I've seen FB videos around YouTube, and was instantly drawn in by how genuine and down-to-earth Kelli and Daniel are.

I'm female, 15 years old, 5'4, and around 59 kg. This is, I guess, a "healthy weight," but I have belly fat I want to drop, and I'd also like to get stronger and build endurance.

I can't really afford to purchase any programs or equipment, so I've been doing HIIT (difficulty of 3-4) with no equipment.

I used to have a pretty unhealthy obsession with food - I would count calories on MyPlate and set a 1200 calorie goal. But some days, I would aim for a net negative amount of calories consumed. I'd try to starve myself, almost. When I went to sleep feeling hungry, I'd feel proud of myself, because I thought it meant I was getting skinnier.

So that's a bit of my history. Since discovering FB, I've taken a lot of the advice to heart, and I've overcome my unhealthy views towards food. Please don't worry about me :)

Basically, I just want to ask your advice on which steps to take in order to achieve maximum results (losing belly fat and increasing endurance). As per my situation, I currently have no access to workout equipment or money to purchase any programs. Advice is much appreciated! Thank you all