I wasn't biligual as a child, but I am now at least.
For me, from the moment on I was able to not only communicate, but also think in both languages, a lot changed.
Certain concepts click together easily in one language, but if I had to use the other language to grasp them, I'd get stuck. And it's not always my first language which is superior, as you might expect.
Each language brings with it a different way of thinking, the cultural aspect, that's coded into it.
It's very helpful to switch between languages for different tasks. Kind of like using mutiple virtual desktops.