Flat and crispy graphics

Im trying to create a mobile game that has flat, bright colors and I want every place to be lightened the same. Like this game:

and this is my game's current state:

I don't know what the problem is. It is too dark and not as good-looking as the first image. If i increase the light, it gets bright, not saturated and crispy. Maybe wrong lighting or wrong material usage? First image looks so crispy and it almost like a Vector art. I modeled all of the assets myself in Blender. I tried using Ambient lighting but it didn't work. I also turned off shadows but still the same. Also there is a distortion in the big red circle i drew and i don't know why is it hapening. And i don't want the shiny light in the little red circle.