How to get a flat stomach fast?

I weigh 106 and I’m small, but I have a little belly fat, so the other day I started to do sit ups to help lose it (I’m starting at 25 sit ups twice a day, so a total of 50) How long should it take to lose the belly fat? And will this help?
Thanks.

Also, if you have any recommendations how I could lose belly fat easily, but also healthy, feel free to tell me (: